Scientists have identified a clutch of subtle genetic changes that have shaped our minds and bodies into the unique form that sets humans apart from chimpanzees and the rest of the animal kingdom…
The findings offer up the humbling conclusion that the secret of human success may owe more to what we lost along the path of evolution, rather than anything we gained.
When the human genome was first deciphered more than a decade ago, some scientists expected to find extra genes that explained why humans had an intellectual edge over their closest living relatives and other species. But since diverging from chimpanzees around seven million years ago, it turns out that our human ancestors lost several hundred snippets of DNA, which together led to traits that are uniquely human, the researchers claim.
In ditching these chunks of DNA, our ancient ancestors lost facial whiskers and short, tactile spines on their penises. The latter development is thought to have paved the way for more intimate sex and monogamous relationships. The loss of other DNA may have been crucial in allowing humans to grow larger brains.
Intriguingly, hardly any of the lost DNA was from genes, which make the proteins that are the building blocks of life. Instead, the missing DNA came from areas of the genome that regulate where and when certain genes are active…
In the years since the human genome project was completed it has become clear that humans and chimps share around 96% of their DNA. Of the three billion pairs of “letters” that make up the human genetic code, genes account for less than 2%.
The US team compared the complete human genome with sequences from the chimp, macaque and mouse. They found that humans lack 510 short sections of DNA that are present in the other animals. Intriguingly, only one missing piece of DNA affected a human gene directly. The vast majority of lost DNA disrupted parts of the genome that control how genes are expressed.
One missing section of DNA was found to block a gene that, in other animals, stifles the growth of brain cells. Losing that DNA may have been a pivotal moment in human development, as it allowed parts of the human brain to expand into the most complex organ known.
Writing in the journal Nature, the researchers describe how our ancestors lost another piece of DNA that gives rise to both facial whiskers and sensitive spines on the tip of the penis, both of which are found in chimpanzees and other non-human primates.
Penile spines – which make the penis more sensitive and speed ejaculation – are more common in animals that face intense competition for mates, and where females are likely to mate with many males in rapid succession.
The loss of penile spines may have allowed our ancient ancestors to copulate for longer, a development thought to have nurtured monogamous couples and paved the way for more complex social structures.
Social structures – too complex for human beings who might not yet have gotten up to comprehending evolution, yet. Sooner or later, education on a global scale will have to back up – and play catch up – with reality and science.
Meanwhile, I look forward to some of the world’s cartoonists commenting on this latest finding. Though every nation’s moral majority will curse the rest of us to perdition, this latest advance in the genetics of evolution cracks a smile easily as a pensive frown.