The Elements of Evolution (5-1) Mass Extinctions Non-Selective


Mass extinctions are generally non-selective. The species that go extinct or are diminished are not those ill-adapted; just unlucky. The most evolutionarily advanced species may have their candles snuffed by the stiff wind of an extinction event, leaving behind lesser-but-luckier life.

The only selection factor in extinction events is tolerance to adversity. The hardiest organisms tend to be the most archaic: little ones that have persevered through tough times before. That withstanding, microbial species do go extinct.

Most bacterial lineages ever to have inhabited this planet are estimated to be extinct. ~ microbiologist Stilianos Louca et al

The safest place to be during an extinction event is the deep ocean. Benthic life fares better than anywhere else.

Mass extinction is typically followed by high species origination rates within a few million years. The availability of nutrients is a key factor in the revival of life.

Glaciation is a particularly subtle seeding for the next generation of species. Organic remains from the previous period are preserved by the cold, only to be released when the ice melts. At the other extreme, heading to hothouse by global warming provides no such head start.

Environmental change correlates closely with extinction but not with speciation. ~ American geologist Steven Holland