The Elements of Evolution – Homo


Here were a number of distinctive, perhaps short-lived, species of proto-humans living in both eastern and southern Africa in the period between 2 and 1 million years ago. ~ Australian anthropologist Colin Groves

Homo (“handy man”) (2.8 MYA–now). This chapter in human history remains especially controversial. Dating techniques alter timelines, while new fossils finds fuel old disputes about lineages and where species boundaries lay. Who says you can’t change the past?!

Most species put under the Homo genus were only somewhat like the hominins that became human: not in the direct lineage that led to moderns. Homo has been treated by anthropologists not as a clade or genera, only as an evolutionary jumble of approximate similarity, with arbitrary distinction from other genera, especially australopiths. From a classification standpoint, Homo is an inexcusable mess.

Throughout the 20th century, the definition of Homo was expanded to accommodate fossil specimens increasingly remote from Homo sapiens in both time and morphology. ~ American paleoanthropologists Susan Antón, Richard Potts, & Leslie Aiello

From the mid-19th century the study of hominids bristled with self-appointed experts. In the late 1850s German physiologist August Franz Mayer identified Neanderthal remains in northern Germany as a Cossack soldier with rickets who had died in 1814 and somehow become buried in 2 meters of fossiliferous earth. Thomas Henry Huxley, friend of Darwin and staunch advocate of Darwinian evolution, happily agreed that the features of Neanderthals fell within the range of variation of Homo sapiens. This was but the start of a trend to buttress Darwin’s conception of human descent as linear.

We can sit in the present and tell stories of the past that make sense of our modern-day adaptations. But these could have evolved for reasons we don’t know. ~ American anthropologist Andrew Barr

A partial hominin mandible found in 2013 pushed back the first appearance of Homo to 2.8 MYA. The supposed spur to its emergence was increasing aridity in east Africa. The specimen represented a slight transition from Au. africanus toward Homo.

50 years after the recognition of the species Homo habilis as the earliest known representative of our genus, the origin of Homo remains clouded. This uncertainty stems in large part from a limited fossil record, especially in eastern Africa. ~ American anthropologist Brian Villmoare et al

The Paleolithic

The problem is that there’s not a huge amount of evidence for anything in the Paleolithic. ~ Australian archeologist Rachel Wood

The Paleolithic (aka the Stone Age) is supposedly the first prehistoric period of human history, beginning with the development of the most primitive stone tools. The obvious omission is ignoring the employment of wood tools, which were doubtlessly used for many millennia before hominids managed flint. The problem is that wood tools were not preserved in the fossil record.

The first hominin to use stone tools was Au. afarensis, who was cutting with stone implements ~3.4 MYA – so the Stone Age rightfully predates the appearance of Homo.

The Paleolithic is a supposed to be cultural period, not a geological one. The Paleolithic lies within the Pleistocene geological period, which spans the Earth’s recent rounds of repeated glaciations. 11.7 TYA the Pleistocene gave way to the Holocene: the interglacial period that continued to the industrial age of humankind.

Unstable climate conditions favored the evolution of the roots of human flexibility in our ancestors. The narrative of human evolution stresses the importance of adaptability to changing environments rather than adaptation to any one environment. ~ Richard Potts

The Lower Paleolithic (aka Old Stone Age) dates from these first stone tools until 200,000 years ago, with the advent or more sophisticated stone tools, such as hand axes and cleavers. The Middle Paleolithic (Middle Stone Age) extends to ascent of early modern humans (aka Cro-Magnon). The Upper Paleolithic (New Stone Age) is associated with Cro-Magnon. Its close coincides with the end of the Pleistocene.

The idea that the origin of Homo is part of a climate-caused turnover pulse doesn’t really bear out when you carefully look at the evidence and compare it against other possible explanations. ~ Andrew Barr

Homo habilis

A so-called “handy man” showed up in east Africa 2.3 million years ago: Homo habilis (2.3–1.4 MYA). H. habilis is assumed to be the direct descendant of Australopithecus garhi, which lived 2.5 MYA.

H. habilis was short, gracile, with long arms, though with a less protruding face than Au. garhi. Brain capacity was 600–700 cm2.

The stone flake tools made by H. habilis showed technical skill, though these tools were probably used for scavenging rather than hunting or defense. H. habilis was no master hunter. Instead, H. habilis frequently fell prey to large predators, such as Dinofelis, a jaguar-sized saber-toothed cat of the time.

Debate continues as to whether H. habilis was in the lineage that led to modern humans. When H. habilis was first declared, some fossil anthropologists wondered out loud whether there was enough evolutionary space between australopiths and later Homo for there to be a species in between (this when the idea of a single-species hominin lineage had its hold). Ironically, with more discoveries, the question was turned on its head: whether H. habilis as classified has too much variability to be a single species.

 Not Homo?

A genus is typically defined as both a clade and a grade. A clade is of lineage, while a grade is of similarity. Snakes are in the same clade as lizards, as they share a common ancestor, but, lacking legs to walk on, snakes are a different genus than lizards by grade.

It is arguable that H. habilis belongs in the Homo genus. H. habilis had a less protruding face than australopiths, as well as other physical distinctions, so does not belong within Australopithecus. But, with its short body, long arms, and other dissimilarities, H. habilis was also physically divergent from H. sapiens, and so is not the same grade as modern humans. The diversity of fossils attributed to H. habilis, and divergences from later Homo, illustrate the difficulties of tracing human descent.

Splitting & Lumping

It is hard to avoid the conclusion that under current taxonomic practice there is a distinct tendency to under-estimate the abundance of species in the primate, and notably the hominin fossil record. ~ American paleoanthropologist Ian Tattersall

Unless an animal can be observed, it is only a guess the degree to which anatomical variances define speciation. By their nature fossils forgo that inquiry; whence arose the constant controversy in paleoanthropology: how to split species versus lumping specimens together.

There were either multiple species of early human, such as Homo habilis, Homo ergaster and Homo rudolfensis, or one highly diverse species. ~ English paleoanthropologist Jay Stark

The frequent paucity of fossil specimens at any one site makes determining Homo speciation difficult. The geographic range of these hominins compounds the accounting for differences found. There is accumulating evidence of diversity in body sizes within early Homo populations, as is seen among modern humans. This augurs for fewer species (assuming you consider the sizable diversity of Homo sapiens to be a single species).

Homo antiquus

In 1984 American paleoanthropologist Walter Ferguson decried Australopithecus afarensis as a species. At the time, the known fossils of Au. afarensis came from sites in Ethiopia and Tanzania.

The considerable variation in the bones of this combined collection were generally thought due to size differences between male and female members of the species. But Ferguson believed the bones belonged to more than 1 species. Based on the size and shape of molars, Ferguson concluded that some of the larger jaws matched those of Au. africanus, while the littler jaws had smaller, narrower Homo-like teeth. The 3-million-year-old fossils were too old to fit with any known Homo, so Ferguson named a new species: H. antiquus.

Ferguson’s species splitting had a larger implication: if Australopithecus and Homo lived side by side for hundreds of thousands of years, it was unlikely that australopithecines were the direct ancestors of Homo.

However merited, Ferguson’s work did not convince to consensus. Au. afarensis is still around, while few have ever heard of H. antiquus.


Beginning in the late 1920s, pioneering English paleoanthropologist Louis Leakey started a dynasty of fossil hunters. He was keen to split specimens into species based upon modest anatomical differences. The resulting plethora of names in the hominin record proved too much for Yale paleoanthropologists Elwyn Simons and David Pilbeam. In 1965 they rationalized the clutter by lumping specimens together into a mere handful of species. The lumping paradigm took hold in the academic community, so much so that lumping led to the single-species hypothesis: that only one variety of hominin existed at any one time.

Despite the demise of single-species sophistry, lumping remains the prevailing paradigm. Richard Leakey followed in his father’s footsteps of liking speciation but has been much more cautious in finding new Homo species.

Easing a specimen within a species is much easier than facing a fight by declaring a new one. Darwin anticipated this problem.

A naturalist will in the end generally be enabled to make up his own mind which to call varieties and which species; but he will succeed in this at the expense of admitting much variation, and the truth of this admission will often be disputed by other naturalists. ~ Charles Darwin

The hominin family tree is likely to be much bushier than the one currently drawn. Some so-called hominins may have been hominids instead.

How can practitioners in this field possibly expect to be able to accurately identify fossil species based upon a few teeth, jaws, and lower faces in light of what we know about the great variation found among different individuals in a single living species? ~ American paleontologist Tim White

Depending upon how one rolls the bones, there may have been as many as 6 contemporaneous Homo species ~1.9 MYA. Their habitats probably overlapped.

Because the geologic dating is so coarse, we can’t yet be entirely certain that these species were in the same places at the same times. Even so, it is perfectly possible that they were interacting. ~ Bernard Wood

Homo rudolfensis

The problem is that there are precious few fossils of either H. habilis or H. rudolfensis, especially from the neck down. ~ Ann Gibbons

A handful of representative fossils suggest that H. habilis had company 1.9 MYA. H. rudolfensis has been identified as a separate species from H. habilis based upon fragmentary evidence that indicates a different hominin.

H. rudolfensis is named after Kenyan Lake Rudolf, where its fossils were found

Compared to H. habilis, H. rudolfensis was larger and had a bigger brain. With a jaw indicating better chewing ability, H. rudolfensis may well have had a different diet.

It could be a Homo habilis, but it could also be another species. ~ Bernard Wood

Homo helmei

Human history commenced at a very much later date in South than in East Africa. ~ T.F. Dreyer

A partial skull was found in Florisbad, South Africa in 1932, dated 259 thousand years old. Its discoverer, paleoanthropologist T.F. Dreyer, declared it a new species – H. helmei – based upon its admixture of early Homo sapiens and more archaic features. While some researchers think many of the African hominin fossils from around this time should be lumped into H. helmei, others tuck this oddity into the lump known as H. heidelbergensis.

Homo gautengensis

Homo gautengensis (2.5–0.6 MYA) lived in south Africa during the residence of H. habilis in east Africa; emerging earlier and lasting longer. H. gautengensis has been described by Australian anthropologist Darren Curnoe as “small-brained” and “large-toothed.” It walked on the ground with 2 feet but probably spent a lot of time in the trees.

H. gautengensis ate a lot of vegetable matter, crafted and used wood and stone tools, and may have even mastered fire. Burnt animal bones were found near H. gautengensis remains.

Homo erectus

The morphology of bones attributed as Homo erectus (2.5 MYA–30 TYA) is extensively variable – hence, uncertainty and controversy as to how divergent the species may have been. Brain size was 750–1,300 cm2 – itself a considerable range.

The H. erectus lifestyle was of small bands foraging and hunting. Like H. ergaster, H. erectus contemporaneously crafted crude stone hand axes. H. erectus also created abstract art: doodling designs on seashells, for instance.

Tenuous evidence suggests areas set aside for specific purposes: sleeping quarters and workshops. ~500 TYA, hearths appear, where a fire was maintained.

H. erectus may have been the first hominin to use boats and rafts to traverse the seas. An inveterate mi-grant, H. erectus spread from Africa 2.0 MYA to Europe, India, China, Indonesia, and possibly Australia. The migration of H. erectus to Indonesia likely occurred at a time when the Sunda Shelf was exposed or quite shallow: 1.25, 0.9, and 0.65–0.45 MYA.

Homo ergaster

Homo ergaster (1.9–1.4 MYA), was as tall as modern humans, with a similar build, and much the same feet. Brain size was 600–910 cm2. H. ergaster lived in east and south Africa.

The classification, ancestry, and progeny of H. ergaster remains controversial. H. ergaster is widely considered the direct ancestor to later hominins: H. heidelbergensis, H. neanderthalensis, and H. sapiens. H. habilis is the putative ancestor of H. ergaster. Whether H. ergaster and H. erectus are separate species is still debated. They had slightly different skull bone structures near the eyes (supraorbital foramen) and H. ergaster had a thinner skull.

With a vertical posture built for long distance travel, H. ergaster became less hairy and evolved better sweat glands, improving endothermy. Panting respiration was replaced by controlled breathing, opening the way for more robust sound production. H. ergaster appears to be the first hominin with humanlike vocal cords. Altogether, the scenario seems of more communication at some distance rather than just at close quarters.

H. ergaster was an innovative stone tool maker, developing the bifacial ax 1.76 MYA. Such axes were used for cleaving a variety of materials, including animal hides and vegetative matter. Some were doubtlessly employed as weapons. Given the large volume of finds in the archeological record, these skills appear culturally transmitted.

Compared to australopiths, sexual dimorphism was reduced by about 20% in Homo generally. The sex size difference in H. ergaster exceeded that of modern humans.

Homo georgicus

Excavations at Dmanisi, Georgia yielded 5 hominin individuals and other fauna fossils, along with Oldowan Stone Age artifacts, all dating 1.77 MYA. This is the earliest hominin discovery in Eurasia.

One of the most intriguing finds was of an elderly person who had lived for some time without teeth. To survive in such a condition this oldster must have lived in a supportive social group.

The first fossils found led to declaration of a new species: H. georgicus. Finding further fossils revised that to a proclamation with far-reaching implications as to hominin classification.

 Lumping, Take 2

We can tell species apart based on differences in the shape of their skulls, especially their face and jaws, but not on the basis of size. The differences in their skulls suggest early Homo divvied up the environment, each utilizing a slightly different strategy to survive. ~ Susan Antón

From the look of it, H. georgicus appears an intermediate between H. habilis and H. erectus. That is only the beginning of the story.

Like the H. erectus fossils that have been found, the Dmanisi specimens exhibited considerable discrepancies. One adult male skull had a large jaw and small brain case: just 546 cm – the size of Au. sediba. Others had brains up to 25% larger, but smaller jaws.

Despite that, there were underlying similarities in skull structures. All told, the Dmanisi variations appear no greater than that found in modern humans or chimpanzees.

H. erectus has been found in disparate places and dat-ed to distinct times. In contrast, the Dmanisi specimens seem anthropologically contemporaneous. Hence, despite the wide grade, that the Dmanisi hominins were a single species seems reasonable.

The 5 Dmanisi crania exhibit derived characters of H. erectus, but also retain some primitive characteristics, including small brain sizes (538 to 750 cm3), suggesting they are part of an early dispersal of that species. ~Susan Antón, Richard Potts,  & Leslie Aiello

The Dmanisi find provoked some researchers to declare that H. georgicus and H. ergaster should all be lumped in with H. erectus, as a single species. Such a sweeping conclusion alters the overarching view of human descent.

If this Homo erectus was a single species, it had a tremendous intercontinental range, especially compared with hominin primate ancestors: apes. Chimpanzees reside only across a narrow band of sub-Saharan Africa. Even in such a small range, ape species have tended to split apart.

2 MYA, the Congo River formed a bend that cut off chimps in the southern part of the range from easy access to their relations in the north. These southerners evolved into the smaller, peaceable bonobo, proving a considerable contrast to their more aggressive erstwhile kin.

Baboons tell a much different speciation story. The largest Old World monkey genus lives across much of Africa and in the Middle East. From place to place, baboon groups look so different as to easily deserve the nod to speciation. A half-dozen baboon species have remained distinct for 4 million years. Some of these different baboons have overlapping ranges. When they come into contact, they regularly interbreed, birthing healthy hybrids. Yet the troops, and species, remain separate, never blurring together. Much of this owes to different lifestyles. Some survive in the desert, while others are woodland dwellers.

The radical proposal to subsume the well-established taxa H. habilis and H. rudolfensis into H. erectus warrants careful scrutiny, and in my view the presented evidence is weak. It is doubtful whether analyses of overall cranial shape have the diagnostic power to distinguish between closely related taxa, as is indeed demonstrated by some of the analyses presented. Species are defined by specific morphological features, not by overall cranial shape. ~ English evolutionary anthropologist Fred Spoor

Taxonomic diversity sustained by ecological differentiation characterized Homo between ~2.0 and 1.4 MYA. 3 distinct lineages of early Homo in Africa remains the most compelling hypothesis. ~ Susan Antón, Richard Potts, Leslie Aiello

Leaning toward lumping may be a simplification of the dynamic of diversification and occasional melding that appears to have been typical among hominids. Fossil specimens repeatedly show a mixture of features which indicate interbreeding between distinct populations (nominally species). This practice appears to be consistent throughout hominid history.

Modern humans migrating into new regions must have interbred with the archaic populations already present in those regions. ~ American anthropologist Laura Shackelford

Outliers keep being found, leaving lumping as nondescriptive, if not problematic. Finds in Spain of 400,000-year-old hominins present a mixture of Homo heidelbergensis, Denisovan, and Neanderthal traits. It suggests that interbreeding among Homo species (or subspecies) was common.

DNA examination of Melanesians indicates an admixture which includes a hominid group for which fossils have yet to be found. Thanks to rampant interbreeding, the descent of humankind is exceedingly complex.

No one knows what to make of this. ~ Ian Tattersall

If anything, splitting would be more informatively appropriate.

Classification is complicated by the apparent fact that hominids were often extensive travelers who had sex with most everything they could. The randiness of modern males has deep evolutionary roots (not to slight lusty women).

Dupes for confusion, there are no agreed-upon criteria by anthropologists to determine speciation. Centuries of classification have yielded no sensible consensus. This is likely to continue.


Species of early Homo were more flexible in their dietary choices than other species. Their flexible diet was aided by stone tool-assisted foraging that allowed our ancestors to exploit a range of resources. ~ Leslie Aiello

Apes tend to have large guts: a trait associated with an essentially herbivorous diet of low-nutrient vegetation. The same applied to early australopiths.

One of the shifts that started with later australopiths – but came to prominence with Homo – is a change in the digestive system. By 1.8 MYA hominin gut size had shrunk.

Tooth size also shrank. Homo is the only primate where the size of teeth dwindled as brain size grew. That must have reflected a change in diet.

In general, gathering and hunting groups live largely by gathering. Hunting is a difficult and hazardous activity with only intermittent rewards at best. ~ English historian Clive Ponting

 Meat & Vegetables

Evolution in the hominin gut owed to a better diet and/or improved digestion. An amalgam of adaptations is likely to have been involved.

Scavenging was always part of hominid foraging. Early Homo retrieved heads left untouched by big cats and devoured the brains. In contrast, hunting required weapons.

Homo erectus was the first hominin that approached modern humans in stature, brain size, and chewing equipment. It appeared 1.5 million years before cooking became a common occurrence.

Stone tools made the difference. To improve mastication, early Homo pounded tubers into paste, chopped greens, and pummeled meat into small pieces.

Raw meat is tough and practically impossible to break down into swallowable pieces just by chewing it. ~ American evolutionary biologist Katherine Zink & American paleoanthropologist Daniel Lieberman

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Children are famously finicky about the greens they eat. It is a behavioral adaptation to a world where lots of plants are toxic. Phytophobia likely has a long lineage in hominids as an evolutionarily instilled precaution.


Plant foods containing high quantities of starch were essential for the evolution of humans. ~ English evolutionary biologist Karen Hardy et al

Much has been made about increased meat consumption driving greater brain wattage in early Homo by those ignorant about animal intelligence in general and human nutrition in particular. If anything, a diet of carnivorous scavenging would have rendered hominins no smarter than vultures (no insult to vultures intended). Even now, eating meat creates an unfavorable gut microbiome, degrading health and promoting mortality.

Any flesh early Homo consumed would have been raw meat, as cooking had yet to be discovered. The derived nutritional value would have been less than meat seared by heat, and it would have borne a serious risk of pathogens – a risk that survivors would take note of.

The optimal diet to feed the body and brain is from plant sources, high in carbohydrates with appropriate protein.

Hominins may have upped their protein intake a bit by eating grubs and adult insects. The often-bandied conclusion that a meat-heavy diet provoked Homo evolution, particularly cognitive advance, is absurd.

Instead, hominins probably became better foragers, having learned through experience and culture the nutritional and medicinal values of plants and their products. Mashing tubers and other root vegetables, with their ample carbohydrate content, may have been significant. This better explains the evolution of hominin guts and brains.

Protein-laden muscle mass – meat – digests down to animal fat and amino acids: not an apt energy source. Further, the acidic digestive environment and indigestible waste products from eating meat tax the system terribly.

Autophagy – recycling proteins, amino acids, and other nutrients from spent cells – provides considerable readily available structural material needed by the body. Autophagy plays a critical role in body maintenance and longevity. Even slight adaptations in autophagy could account for hominin gut changes.

The hominin brain has long required a lot of energy. That energy has always been supplied by plant foods: high in carbohydrates and providing a surfeit of balanced protein.

Archeological evidence points to hominin descent on a largely vegetarian diet. For one, foraging is much easier, and more reliable, than hunting.

2.3–1.2 MYA, Paranthropus was a robust savanna forager that had a varied seasonal diet, preferring fruit and nuts when available, but resorting to herbaceous vegetation when not – not dissimilar to lowland gorillas. While Paranthropus had a head, jaw, and teeth comparable to a gorilla, it did not have the gorilla gut.

2 MYA, Au. sediba, the last australopith, was a gracile omnivore with a small gut that harvested from the woodlands: living off fruits, nuts, leaves, and sedges, as well as plants such as papyrus or cypress. Small critters, including insects, were likely on the menu. Au. sediba‘s diet, while perhaps higher quality, was not strikingly different from that of chimpanzees.

Homo ergaster (1.9–1.4 MYA) – a putative ancestor to humans – was another omnivore with a small gut. Archeological finds of axes and hides suggests skinning animals, likely for clothing. How much raw meat H. ergaster ate is not known. A safer, more readily available fare was plant tubers. These tough but highly nutritious vegetables were likely processed with stone tools to require less chewing and render them more digestible. As with humans today, juicy tubers and roots were probably an important part of H. ergaster‘s diet, providing ample carbohydrates and protein in a wholesome balance.

Considering the health risks of a diet high in raw meat, and the relative ease of finding vegetative food, it is most likely that a more learned selection of plant produce played a dominant role in the descent of humans, especially before the advent of cooking.

Neanderthals were more inclined to carnivory than other hominins. That dietary preference may have been instrumental in their demise, as its tax on health limited their life at the same time their competitor – Cro-Magnon – was starting to have a significantly longer life span. Longer life meant greater cultural transmission between generations.

The value of steeped experience cannot be overestimated. Elephant groups are led by an elder matriarch. A group bereft of senior leadership fares poorly by comparison.

Seafood shows up on the menu much more recently than other meat. The Chinese were supplementing their diets with freshwater fish 40 TYA, but contemporaneous Mediterranean settlers ignored any watery bounty.


Who lit the first figurative match is hotly contested, but someone overcame innate fear of flame to harness its observed power. H. erectus or H. ergaster might have been the first to master fire 1.7 million years ago, perhaps earlier.

Controlled use of fire was a breakthrough technological advance, providing light and heat for many uses.

In breaking down plant cell walls via heat, cooking made vegetables more nourishing by unlocking their nutrients. The same applies to meat.

Fire was also used to drive game, and so make hunting easier. Later, with the onset of agriculture, fire cleared woodlands to make way for crops. This practice has continued to the present day. In grossly degrading the environment, fire was humanity’s first Faustian bargain.

Fire was also a means for further socialization, becoming a symbol in various belief systems of purity, sacrifice, or damnation. Fire was one of the 4 primordial elements, along with water, wind, and earth. Fire became embedded in hominin culture as well as providing for population increase and territorial expansion.

The combination of cooperative hunting with weapons, along with cooking and sharing, is ubiquitously recognized as a milestone in hominin evolution, notably the social recognition of the power in cooperation. That milestone was probably met around the time when spearheads were developed, some 500 TYA.

Homo antecessor

Hominins reached Europe by 780 TYA, probably earlier. H. antecessor (1.2–0.8 MYA) may have been the first home-grown European species. The fossil record is sketchy, but H. antecessor looks to have been of similar stature to modern humans, albeit longer, more slender arms and a wider chest. Stone tools found nearby suggest they were used for skinning carcasses and woodworking. Evidence suggests that H. antecessor practiced cannibalism.

Homo heidelbergensis

H. heidelbergensis (600–200 TYA) was more technologically savvy than H. antecessor. They made better tools, which were used for hunting and food preparation.

Whether H. antecessor and H. heidelbergensis (0.6–0.2 MYA) were the same or distinct species is still debated, though H. heidelbergensis is generally considered a separate species. Both descended from H. ergaster.

H. heidelbergensis had an extensive habitat: ranging from southern Africa to northern Europe and into Asia. It may have been the first hominin to gain a permanent foothold in Europe, though it was not the first to try.

H. heidelbergensis was tall: males averaged 1.75 me-ters and were more muscular than modern men.

Their jaw was well-built for chewing, albeit with smaller molars than earlier hominins. This was a trend toward more modern humans.

Some discovered skeletons show evidence of disease and healed injuries. Life was doubtlessly difficult in Pleistocene Europe. The majority of H. heidelbergensis fossils found have been of teenagers. H. heidelbergensis may have been the first hominin to bury its dead.

Taking advantage of good weather, H. heidelbergensis spread from Africa into Europe by 700 TYA, placing progeny that would spawn the Neanderthals. Later, the Cro-Magnon who came to Europe some 45 TYA interbred with the natives. Both were the issue of H. heidelbergensis.

Darwin hypothesized that all human races descended from a single species (monogenesis). Instead, humans descended from multiple species. As a breed, human beings are mutts.


Let the species die. ~ Spanish paleoanthropologist Juan Luis Arsuaga

While a cogent description can be made for H. heidelbergensis, the attribution has a history of controversy. The species is based upon a single 600,000-year-old lower jaw found in Mauer Germany in 1907. Nothing quite like it has been found since.

It took decades for the species designation to catch on. Disparate finds of roughly similar archeological age – skulls with distinctive thick brow ridges and large faces – convinced numerous paleoarcheologists to lump the specimens together under the H. heidelbergensis banner.

H. heidelbergensis was conceived as having a large brain, and having mastered complex tools, based upon bones and wooden spears found at a dig in Schöningen Germany.

Another faction was never convinced. They thought H. heidelbergensis was a concept, not a species. Some of the fossils attributed to H. heidelbergensis were instead Neanderthal, they contended.

Lumping into H. heidelbergensis creates the monogenesis that Darwin dreamed of. In contrast, the demise of H. heidelbergensis would mean a plethora of hominin intermediary specimens, with no clear single-species lineage to humankind. If all the finds attributed to H. heidelbergensis are not a single species, the descent of humans becomes even more of a tangle. That may well be.

The H. heidelbergensis controversy is far from being a singular example that hominin evolution appears an exercise in adaptive radiation spread across continents, with occasional interbreeding that entangled the Homo genus as a mosaic of species.

Homo rhodesiensis

Tom Zwiglaar, a Swiss miner, found a partial hominin skull and other bone fragments in 1921 while working a lead and zinc mine in northern Rhodesia (now Kabwe, Zambia). The skull was dubbed Rhodesian Man at the time of the find.

Rhodesian Man got dated 300–125 TYA, and estimated to be a young adult, with heavy tooth wear from eating abrasive foods: grains, tubers, and rootstalks. The teeth show the oldest occurrence of cavities for a hominin. This young Rhodesian Man died of either a dental infection or chronic ear infection.

Similar remains of the same or earlier time have been found in faraway places: in east Africa (Bodo, in Ethiopia) and the southwest tip of South Africa (Saldanha).

Tools found at Rhodesia were made of chert and quartz, worked on both sides. A granite ball was shaped into a sphere, which might have been used for grinding food.

The finds at Bodo and Saldanha also included an assemblage of tools, including bifacial hand axes and other specialized implements. Cut marks on the Bodo skull indicate that it was defleshed after it died, though for what purpose is uncertain.

In several respects H. rhodesiensis resembles H. heidelbergensis, which is where Rhodesian Man has been lumped.


The Neanderthals trod lightly and relied as much on their powers of observation and quiet imprint on the land as they did on their technology. ~ English anthropologist Brian Fagan

Neanderthals (H. neanderthalensis) (800–45 TYA) were modern humans’ closest relative, living in Europe and western Asia. No Neanderthal fossils have been found in Africa.

Descending from H. habilis or H. erectus, who arrived in Europe well over 1 MYA, Neanderthals arose during glacial cold, then lived through severely variable climes that made for tough times. Neanderthals occupied a broad swath stretching from Portugal to Uzbekistan.

Other hominin species lived near Neanderthal. In a case of convergent evolution, the African H. rhodesiensis evolved separately from the Eurasian H. neanderthalensis.

Neanderthals evolved in fits and starts, which was typical of hominins. Neanderthals adapted first to diet and climate early on. Incremental brain changes came later, convergently independent of the human lineage.

Though similar to Homo sapiens, Neanderthal were slightly shorter and more robust: muscular, barrel-chested, with stocky limbs that conserved body heat. Like modern humans, most Neanderthals were right-handed.

Neanderthal bodies were better adapted for a colder climate than earlier African hominids. But more than build was required to endure frosty weather.

Long distance running adaptively evolved in African hominins, where the savanna made it advantageous. In contrast, Neanderthals were better built for hiking in the woods. Like some lemurs, baboons, and other hominins, Neanderthals lived in caves and rock fissures where available. They resided in homes with a hearth.

Neanderthals had mastery over fire. They wore animal pelts to keep them warm.

Unlike their African ancestors and later cousins, some Neanderthal had pale skin, blue eyes, and blond or red hair. Less skin pigmentation helps absorb vitamin D in places with lower sun exposure.

There is no reason to assume that the biological differences between Neanderthals and modern humans necessarily translated into differences between their intellectual capacities. ~ Spanish anthropologist Camilo Cela-Conde & Spanish-American biologist Francisco Ayala

Neanderthals were tribal, with strong family groups, often patrilocal: males stayed with the group, while women moved into another family.

Neanderthals conversed with each other, had language and culture. They decorated themselves with ornaments and jewelry, probably wore makeup, possibly tattooed themselves.

Neanderthals made etches with the intent of creating a visually harmonious and symbolic motif. ~ Italian paleontologist Francesco d’Errico

Neanderthal artifacts show appreciation of symbolism. Neanderthal created rock art in caves, depicting both representational and abstract designs. Music was part of Neanderthal culture. A Neanderthal bone flute was found that may be as old as 82,000 years. They had rituals. Neanderthals buried their dead in their caves, which implies belief in something beyond the mortal coil.

The evidence for cognitive inferiority is simply not there. The conventional view of Neanderthals is not true. ~ Italian anthropologist Paola Villa

 Neanderthal Brain Development

Neanderthals had 10% bigger brains than modern humans, with a slightly different brain structure. More of the brain was given over to vision and movement processing. Augmented vision processing is typical of modern humans adapted to living at higher latitudes, to cope with generally lower light levels than tropical residents. Neanderthals also had big eyes.

From birth to adulthood, a bonobo brain expands 2.5 times. In contrast, a Homo brain enlarges 3.3 times. As a life-history variable, humanlike brain development originated early in the evolution of the Homo genus.

Large brains require a slow life-history. Later-evolved Homo achieved their big brains mainly through a greater growth rate during early ontogeny, rather than an extended growth period. Neanderthal brains developed more quickly during infancy than those of contemporaneous Cro-Magnon. This pattern resulted in a bigger brain size, though not necessarily an earlier completion of brain development.

The additional energetic cost of a natal fast-growing brain is largely born by the mother. Species investing in big infant brains with a rapid growth rate require large, late-maturing mothers. This slows the pace of life history.

Cro-Magnon evolved slightly smaller bodies and brains than Neanderthals. This was an optimization that quickened the pace of life history, ultimately leading to a higher reproduction rate.

Neanderthals and Cro-Magnon had the same life span. But, partly owing to brain ontogeny, emergent modern humans outbred Neanderthal. It was a telling difference. Population numbers aid species survival when facing adverse environmental conditions.

 Neanderthal Technology

Neanderthals were technologically savvy. ~ English archeologist Annemieke Milks

Neanderthals invented string 90 TYA. Besides tying things together, they strung shells and other ornaments for necklaces.

44 TYA a community of Neanderthals built a large (40 m2), ring-shaped enclosure using 3,000 mammal bones. Many were mammoth bones. The enclosure may have served as a wind break, or as a base for a wooden building. Animals were butchered, roasted, and eaten within.

Neanderthals rationally organized their living spaces, sometimes creating structures within the caves in which they resided. Hearths were placed to take advantage of radiative warmth. To limit injuries, tool workshops were situated away from high-traffic areas, though where light was abundant.

Neanderthals skillfully made stone tools of a quality roughly equivalent to their contemporaneous African cousins, including the humans that would displace them. For one, Neanderthals solved the problem of hafting a stone point onto a wooden shaft to make a spear. One way they attached a stone spearhead onto a staff was by gluing it on using bitumen (asphalt). This is no simple task. A chunk of bituminous rock had to be heated, and the viscous gunk applied so that the spearhead was properly positioned.

Neanderthals were very capable technicians. ~ English anthropologist Chris Stringer

Neanderthals passed their technical skills on from one generation to the next. When groups encountered each other they exchanged knowledge, which influenced later designs.

Neanderthals invented the lissoir: a bone tool used to work animal hides, making them softer, tougher, and more waterproof. In making lissoirs, dear ribs were chosen for their flexibility. A selfsame tool, called a slicker, is used to work leather today. Bone tool technology was learned by Cro-Magnons from Neanderthals.

Besides catching small animals, Neanderthals adapted to ambush-style hunting of big game, such as the woolly rhinoceroses that roamed north-central Europe during cold times. Neanderthal started the slaughter that would leave the continent bereft of large fauna.

Neanderthals were not warriors. There is no trace of warlike conflict among them. This is a most significant distinction between Neanderthals and nascent modern men.

 Neanderthal Diet

Neanderthal diets varied. Those that lived on the plains ate more meat than contemporaneous Cro-Magnon. They also consumed the stomach contents of the herbivores they slaughtered; a delicacy with the consistency and flavor similar to cream cheese.

Forest-dwelling Neanderthals were largely vegetarian. Neanderthal residing near the seashore harvested mollusks, fish, and hunted marine mammals, such as seals and dolphins. Neanderthals also enjoyed cooked vegetables, edible mushrooms, and fresh fruit when it was found.

At least some Neanderthals had sophisticated knowledge of herbal remedies and knew the nutritional value of certain plants. Neanderthal were aware of willow bark for pain relief (the source of aspirin) and knew of fungal antibiotics.

After a meal, a Neanderthal may have used a toothpick to clean its teeth. This technique for fighting periodontal diseases was culturally transmitted.

Physically, Neanderthal were bruisers. Their relatively heavier build meant that they needed a 1/3rd more calories than Cro-Magnon.


Crossing paths in the Near East 120–60 TYA there was repeated interbreeding between Neanderthals and the proto-humans emerging from Africa. Though Cro-Magnon and Neanderthal largely kept to themselves in Europe, with separate communities, interbreeding occurred there as well. Upper Paleolithic skull fossils show a mosaic of Neanderthal and Cro-Magnon features.

When Neandertals and modern humans mixed, they were at the edge of biological compatibility. ~ American geneticist David Reich

Though most Neanderthal genetic input was adaptively removed from modern humans, 2–4% of the DNA in Eurasians today descends from Neanderthals. This genetic influence is equivalent to that of a great-great-great-grandparent. The conferred benefit for descendants of the interbreeding was an improved immune system. Native Africans have no Neanderthal DNA.

Around 55 TYA, Eurasia began to swing wildly between frigid and temperate in short cycles lasting mere decades. The cold snaps brought ice sheets to what had been forests.

Animal populations upon which Neanderthal preyed were devastated. Nonetheless, Neanderthals, though diminished in numbers, adapted to the early rounds of climatic calamity.

The weather got worse: oscillations between warm and frigid becoming increasingly wrenching. The fluxes brought profound ecological shifts in both flora and fauna, as evolution worked double time to keep up. In the course of a single individual’s lifetime, many of the plants and animals were replaced by new species.

Climate problems may have been compounded by resource competition between Neanderthals and Cro-Magnon. That withstanding, it is unlikely that early humans were determinative in the demise of Neanderthals.

The climatic see-saw became too much of a challenge for Neanderthals. Already splintered into small groups, they dwindled and died out ~40 TYA. The timing coincides with a cataclysmic volcanic eruption in Italy, which provoked an abrupt cold spell throughout Europe.


A small portion of a finger bone was found in Denisova Cave in southern Siberia in 2008. A tooth and toe bone were later found. The cave had also been inhabited by Neanderthals and Cro-Magnon. But the finger bone DNA gave genetic distinction to a new hominin, dubbed Denisovan.

Living 500–30 TYA, Denisovans had a shared heritage with Neanderthals. Their common ancestor emerged from Africa half a million years ago. Neanderthals went west, settling in the Near East and Europe, while Denisovans headed east; whence their speciation. Denisovans ranged from Siberia to southeast Asia. Unlike blue-eyed, fair-skinned Neanderthal, Denisovans were brunettes with brown eyes and dark skin. 100–60 TYA, Neanderthal and Denisovan territories overlapped, and the two species occasionally interbred.

70–40 TYA, modern humans met Neanderthal in the Middle East. Humans later encountered Denisovans in southeast Asia. Denisovans lived among and interbred with humans. The genetic makeup of Australian aborigines and Melanesians derive largely from Denisovans.

Homo naledi

A creature that would have walked upright really well but also would have been comfortable in the trees. ~ American paleoanthropologist William Harcourt-Smith

H. naledi lived in south Africa. The remains of 15 indi-viduals were found deep within a cave, not buried in sediment.

H. naledi had a bewildering blend of features: a body mass like that of small-bodied humans and the largest known australopiths; jaws and teeth consistent with Homo, but a small braincase (~500 cm2), even as its skull was shaped like early Homo; Homo-like legs attached to a flared pelvis like that of Au. afarensis; australopith shoulders and ribcage, but with Homo wrists and hands.

Naledi‘s brain was tiny. ~ American anthropologist John Hawks

The H. naledi bones were only 300,000 years old.

It is now evident that a diversity of hominin lineages existed, with some divergent lineages contributing DNA to living humans, and at least H. naledi representing a survivor from the earliest stages of diversification within Homo. ~ South African anthropologist Lee Berger et al

Homo floresiensis

Brain tissue is energetically expensive. A decrease in brain volume may be advantageous to an animal’s survival under the environmental conditions associated with islands. ~ English paleontologists Eleanor Weston & Adrian Lister

H. floresiensis (~0.9–0.05 MYA) is one of the last known hominin species to become extinct. Specimens were first found on the small Indonesian island of Flores in 2003.

While H. floresiensis clearly belongs in the human family as a distinct species, their skeletons are like no other. Nicknamed the Hobbit because its small size, these folk were 1.0–1.2 meters tall, with brains roughly the size of modern guerillas (420 cm2).

Homo erectus reached Flores about 1 million years ago. The hominid population there evolved to be smaller, as is common with island mammal species, owing to limited food resources and other factors.

Small brains were of no consequence mentally. Hobbits made tools as sophisticated as their contemporaries.

H. floresiensis was far from unique. Pygmies in Africa are a similar adaptation. Such small stature in hominins has arisen independently a few times. Like H. floresiensis, H. luzonensis was a hominin that adapted to living on Luzon, a Philippine island, via downsizing. Among the adaptations was better ability to climb trees: a physiological and lifestyle reversion not seen since australopiths.


H. erectus made its 1st foray out of Africa 2 MYA. Its descendants of numerous species – including Neanderthal and Denisovans – spread throughout Eurasia. Some likely returned to Africa, from which came the creatures that supposedly spawned modern humanity.

The human past was highly complex. Population movement, mixing, and local extinction were ubiquitous throughout. ~ paleoanthropologists Anders Bergström & Chris Tyler-Smith

Homo sapiens

“Not all those who wander are lost.” ~ English novelist J.R.R. Tolkien

Humans evolved in Africa by 350–315 TYA. Like hominins before them, they had the traveling jones: spreading across the continent, and into Europe and Asia, in repeated waves. Ancient rivers and green corridors through what is now the Sahara Desert provided passage.

Some of the earliest forays were met by setbacks, as ice ages took their toll. Europe was especially inaccessible. When the weather was favorable, the diaspora was ongoing.

Many early technical innovations were made to facilitate long distance travel, including seafaring capability. These innovations diffused as cultures encountered one another.

Hominins reached California ~130 TYA, at the beginning of an interglacial period. They likely crossed the ocean to get there: an impressively courageous feat.

By 100 TYA, early explorers had expanded into western Asia. The temperate climate of southern Asia made for a relatively easy migration. Some headed east, all the way to the Pacific Ocean.

Moderns reached Australia 65 TYA. The only sign that there was land out of sight were the migratory birds in flight. It was enough.

Men were never ones to sit still. A wave of native Australians returned to the Asian mainland 20 TYA.

Humans first traversed the ice bridge of Beringia 26–20 TYA. People were in South America over 18 TYA.

Interbreeding was ongoing among peoples. The descent of humanity was a complex weave. There was no singular origin of the ‘species’.

 Toba Super-Eruption

Sumatra exploded 74 TYA. 2,500 km3 of magma flowed from the Toba volcano there. The area covered in lava was twice the size of New York City, equivalent to 76% of Rhode Island. Toba was the largest volcanic eruption of the past 2 million years. The 74 TYA Toba explosion was last of 3 major eruptions in the last million years.

Ash spread north and west by prevailing winds, covering the Indian subcontinent and raining down upon the oceans from the Arabian Sea to the South China Sea. All of south Asia was covered in a 15-cm ash blanket.

The Toba explosion coincided with the onset of Earth’s last glacial period, providing additional chill: a volcanic winter which fell global surface temperatures 3–5 ºC.

The effect of Toba on global human populations may have been devastating. Toba seems to have shrunk the gene pool. Genetic evidence suggests that humans today descended from a population base of a few thousand breeding pairs that existed 70 TYA.

Other animals – in at least Africa, Borneo, and India – recovered from low population numbers 70–55 TYA. Humans flowed out of Africa in a major migration wave 70–60 TYA.

 Red Deer Cave People

14.5–11.5 thousand-year-old fossils found in caves in southwest China indicate a distinct hominin lived there until the end of the last ice age. These people were different than Denisovans and modern humans who lived contemporaneously in the same region.

Red Deer Cave skulls were anatomically unique from all modern humans, including those from Africa 150 TYA. Red Deer Cave people had a broad nose, flat face with prominent brow ridges, jutting jaw that lacked a chin, along with a rounded braincase in a thick skull. Their brain size was moderate.

The uniqueness of the Red Deer Cave people suggest that they lived largely in isolation from other human species.

The term Red Deer derives from these people’s apparent taste for venison, whose remains were also found in the same caves. The people roasted these large deer in their home.

The discovery of the Red Deer Cave people shows just how complicated and interesting human evolutionary history was in Asia right at the end of the ice age. We had multiple populations living in the area, probably representing different evolutionary lines: the Red Deer Cave people on the East Asian continent, Homo floresiensis, or the ‘Hobbit’, on the island of Flores in Indonesia, and modern humans widely dispersed from northeast Asia to Australia. This paints an amazing picture of diversity. ~ Australian evolutionary biologist Darren Curnoe


Cro-Magnon is the informal reference to the European human contemporaries of Neanderthals. The term Cro-Magnon derived from the first fossils found in a cave in France called Abri de Cro-Magnon.

Though well-known, the term Cro-Magnon has lost favor among anthropologists. Cro-Magnon has no taxonomic status, as it refers neither to a species or grade. Further, the term has no direct application to an archeological phase or culture. Nevertheless, Cro-Magnon provides a helpful handle for early humans that lived during the Upper Paleolithic, the onset of which neatly coincides with the earliest Cro-Magnon fossil finds in Europe.

The term Cro-Magnon was scotched for European early modern humans – the sort of inelegant mouthful that modern anthropologists seem fond of. It won’t be used here.

The development of early Africans who migrated to Europe and became Cro-Magnon mirrored that of their distant relatives to the north, the Neanderthal: increasing skill with tools, growing cultural and social sophistication.

Neanderthals and Cro-Magnon both fashioned clothes from animal skins but the African immigrants did so with more style and skill; likewise, jewelry.

Cro-Magnon lived in caves and constructed shelters. A typical group was 30 to 50: generally, an extended family group, forming a loose network. These hunter-gatherers fashioned sophisticated stone tools, which, via group coordination, brought down megafauna: feasting on enormous beasts that could feed a growing population. So did Neanderthals.

Cro-Magnon life expectancy was 25 to 35 years. Cro-Magnon infant mortality was 150–250 per 1,000 births, which remained the norm into the 19th century. Infanticide looks to have been a somewhat widespread practice; a presumed population control mechanism.

Cro-Magnon were territorial: a trait that would be taken to extremes in modern humans.

 Cro-Magnons versus Neanderthals

A difference in build and development, along with cultural refinements emanating from division of labor, gave Cro-Magnon an edge in survival over the Neanderthal natives in Europe. Cro-Magnon in the time of their European cousin sewed clothes. Meantime, Neanderthal left no sign of needles or sewn garments. Such skill was symptomatic, not causal, of why Cro-Magnon lived on and Neanderthal did not.

Neanderthal focus on game might have made hunting a family sport: the women spotting and flushing game, the men taking the kill. In contrast, the more varied diet of early moderns would have favored women collecting nuts, grains, seeds, berries, and the like, and preparing them, while the men hunted. Such division of labor may have provided an incremental productivity, at a time when such seemingly modest advantage might have meant the knife’s edge of survival.

Early domestication of females would have garnered a tremendous advantage in both invention and the production of food, clothing, and living essentials, plus acceleration of social skills by a greater variety of activities and interactions. Womanly contributions put Cro-Magnon on a constant learning track, accelerating mental development, sociality, and communication skills. The augmented separation of the sexes was also likely to have been instrumental in the sexism which became integral to human culture.

As the Neanderthals were dying out, the humans who would outlast them started living longer. The number of grandparents among moderns skyrocketed. This meant both more time for acquisition of knowledge and its transfer to the next generation. Greater longevity may well have been a payoff from the improved cultural practices of Cro-Magnon.

A looming factor was purely biologic: Neanderthals were bulky compared to more gracile Cro-Magnon, and so required more calories to survive. Neanderthals had shorter strides, which meant that Cro-Magnon could cover more ground while foraging or hunting.

These efficiencies would have allowed moderns more time for varied skill acquisition and rearing children, both of which would have enhanced survival chances for the young. Today, that virtuous cycle of lean and keen has been lost on post-industrial humans, leading to lower life expectancy and ubiquitous stupidity at a time when education can be had.

Competition and conflict between Neanderthal and nascent moderns appear to have been direct at times. At least one Neanderthal has been found with what appears a spear wound to the chest. The puncture marks were that of a chiseled spear head, a type not known to Neanderthal culture, but used by contemporaneous Cro-Magnon.

A butchered Neanderthal child was found in France which indicated cannibalism by Cro-Magnon. Also found were necklaces crafted from Neanderthal teeth and bones.

Natural resources are never inexhaustible, and hominins have long had a way of working their habitats to exhaustion. By 40 TYA, large game animals were severely depleted in Africa. By 20 TYA, the woolly mammoth, mastodon, saber-toothed tiger, giant bison, and sloth, were all gone from Eurasia. By 12 TYA, over 200 species had been exterminated by man’s intervention. The number of extinct species has since grown so large that men have lost count; not that they ever really cared.

 Continuing Evolution

From early Homo species to archaic Homo sapiens 300 TYA there was a trend toward robustness which finally reached a plateau, then gradually declined. Early humans had thick skulls and muscular physiques. They were incredibly strong. The humans that traveled out of Africa 200,000 years ago were less beefy than those 100,000 years earlier, though more robust than humans today.

Most populations of early moderns gradually became more gracile: a trend that dramatically ratcheted 10,000 years ago, at the end of the last Ice Age. This includes a 10% reduction in brain size: from over 1,400 cm2 to an average 1,300 cm2.

There are exceptions. Some populations, including Australian aborigines, retained relative skeletal robustness. The generally accepted explanation is that hard times made for hard humans.

Early on, muscle mattered more. With more advanced tools, muscle mattered less. The facility to manipulate the environment allowed hominins to evolve into a relatively weak, gracile species.

There were many epigenetic changes in the brain development of moderns. Modern humans are more susceptible to organic mental illnesses, such as autism and schizophrenia, than their hominin predecessors.

There were also numerous changes in epigenetic regulation of genes in the immune and cardiovascular systems. Meantime, the digestive system remained relatively unchanged.

Environmental changes affected early moderns. Some were self-imposed. Exterminating all the local large game necessarily changed strategies for getting food.

Early agriculture was haphazard. The first farmers suffered nutritional stress; a surefire ticket to smaller body size.

Social changes may have played a role, though characterizing how those changes translated to a slenderer physique is speculative. Changes in foraging may have lessened the benefit of strength-based competition between men for mates: size mattered less than resource acquisition, which was more a matter of smarts.

Various forms of agriculture took hold at distinct times in various regions of the world, yet humans tended to become more gracile regardless of where or how they lived.

The one constant for all was an average increase in global temperature from the end of the Pleistocene. A warming climate is likely to have been a causative agent in human downsizing. In many parts of the world, numerous nonhuman animals also declined in size contemporaneously.

◊ ◊ ◊

Human evolution is ongoing.

Pigmentation changes are rather easily accomplished epigenetically. This accounts for the distinctive variations among human subspecies which have emerged.

The thick, straight, black hair that typifies east Asians arose within the past 30,000 years. Red hair has an even more recent origin, as a lightened variant of brown hair.

Earwax and sweat glands, both traits from related genes, have changed in the past 25,000 years. Stinky armpits and sticky earwax are old school. The innovation, found in east Asians, is flakier, drier earwax and less pungent body odor.

In the past 5,000 years, the skin, hair, and eye colors of Europeans have lightened, owing to local climate. Sexual preference for blond hair and blue eyes has made them more common. Meanwhile, Africans in malaria-infested areas developed greater resistance to the disease.

10,000 years ago, human teeth were 10% larger than today. As eating softer cooked foods became the norm, teeth and jaws shrank, generation by generation.

Lactose tolerance is another recent dietary adaptation to consuming dairy products and has independently evolved at least 5 times in different human subspecies in the past 5 millennia. Other adaptations related to consuming interspecific milk, which is not especially wholesome, have also occurred, including in the microbiome.

 Human Speciation

If bounds are used that would distinguish modern humans and their direct ancestors from other taxa, those bounds would exclude many living humans from the taxon. ~ Camilo Cela-Conde & Francisco Ayala

Modern humans are remarkably diverse in both morphology and less-striking physical features, not to mention internal differences which are not visible. Ancestry, culture, climate, and diet are causal factors.

A genome has vast potential for variety. Changes in gene regulation and expression often reap major adaptive advantage.

There was statistically scant change in the genes between the earliest hominin and that of modern humans. There are less than 100 protein-coding gene differences between Neanderthal and modern man.

What was more pervasive were a raft of modifications embodied epigenetically. The rise of moderns was mostly a mass of modest genic tweaks that adaptively aggregated into significance.

Divergence in gene regulation can play a major role in evolution. ~ American geneticist Dawn Thompson et al

Human populations evolved various traits as habitat adaptations: not only because of local pathogens, but also owing to cultural differences which drove genetic diversity. Contrary to anthropologists’ recent proclivity toward lumping, speciation is defined biologically not as inability to interbreed, but unwillingness to do so.

Fish and birds that encounter each other frequently – biologically sexually compatible – choose not to interbreed by preference and are considered separate species. Modern humans have been treated otherwise. Genetic analysis has demonstrated that European Cro-Magnon and Neanderthal interbred, yet both are considered separate species.

By an impartial biologists’ definition, the so-called human ‘race’ comprises a multitude of subspecies (or downright species), separated by both biome and socioeconomic strata, including a classic trait of speciation: tribal behaviors (aka cultural mores) that inhibit interbreeding. Clearly is it easier for anthropologists to speciate hominins of the past than it is to do so with current populations.

Humans tend to mate with those of similar personality, education, social standing, and even genome. Such discriminatory preference is termed assortative mating.

Nonetheless, where peoples converge, interbreeding invariably occurs, albeit in limited numbers. Unlike choosier species, many men are strongly inclined toward sex with anything that is plug-compatible. All around the world, rape remains common.

“If we consider all the races of man as forming a single species, his range is enormous.” ~ Charles Darwin