“Variety’s the very spice of life, that gives it all its flavour.” ~ English poet William Cowper
From an evolutionary perspective, sex is expensive: it necessitates additional bodily resources, and, more pressingly, taxes organisms with energies spent in mating and breeding; you know what I’m talking about.
The benefit of sex is variety. Having different individuals in a population with distinct traits provides a hedge against extinction should the population encounter hard times. When the going gets tough, the outliers just might make it through.
Animals grow by cell division/replication: 2 cells from 1. For growth and bodily maintenance, fresh somatic cells are spawned in a process termed mitosis.
The special, germline cells used for sexual reproduction undergo a process similar to mitosis, but with a critical difference: sex cells are half-complete: haploid. To create an embryo in which a new life begins, sperm and egg cells must combine, and become diploid.
A chromosome is an elaborate package containing genetic instructions (DNA) and mechanisms that facilitate reading the instructions. Chromosomes are the largest and most complex molecule in all of Nature. Each of your cells has 2 copies of 23 chromosomes; 1 copy of each chromosome was inherited from your mother’s ovum (egg cell), and 1 copy from your father’s sperm.
Meiosis is the intricate, multi-stage manufacturing process of sex cells (gametes). Meiosis makes winners and losers out of chromosomes, as only half of the chromosomal entrants go on to become a gamete: sperm or egg cell (ovum). For an ovum, the final stage of meiosis results in a viable egg and another cell, called a polar body, which is expended. Chromosomes involved in sperm production face a selfsame determinative fate. So, chromosomes compete to become a gamete.
“Chromosomes compete with each other for inheritance during meiosis.” ~ American biochemist Francis McNally
At a certain stage of meiosis, chromosomes, attached to a meiotic spindle, are pulled to opposite sides of a cell before it divides. A meiotic spindle is a skeletal structure, built of proteins, that holds the chromosomes in place.
From this point in the process, the positioning of a chromosome determines whether it will become part of a gamete or not. A resolute chromosome that is not in a position to go to the pole of the cell that will become a gamete jiggers a latchkey protein that lets the chromosome prematurely detach from the meiotic spindle. Then the chromosome reorients itself to be in the proper pole position.
“If you’re facing the wrong way, you need to let go so you can face the other way. That’s how you ‘win’.” ~ American cytologist Michael Lampson
Chromosomes know their situation, and react accordingly: intelligent, goal-oriented behavior. Such awareness and strength of will require consciousness and a mind.
“Meiotic drivers exploit the asymmetry inherent in meiosis to enhance their transmission through a process known as meiotic drive.” ~ Japanese cytologist Takashi Akera et al
All this is just within a single cell. The different cells within multicellular organisms must continually communicate and coordinate with each other to properly function.
Further, some host cells in a macroscopic body constantly interface with foreigners, such as resident microbes: the microbiome. That essentially means speaking a foreign language: to exchange the molecular materials each party needs to keep going. In other words, some cells are multilingual.