“Humbling” was the prevalent adjective used by the scientific teams and the media to describe the principal finding – that the human genome contains not the anticipated 100,000 - 140,000 genes (the stretches of DNA that direct the production of amino-acids and proteins) but only some 30,000+ -- little more than double the 13,601 genes of a fruit fly and barely fifty percent more than the roundworm’s 19,098. What a comedown from the pinnacle of the genomic Tree of Life!
The “Head-scratching” Discovery
It was here, in tracing the vertical evolutionary record contained in the human and the other analyzed genomes, that the scientists ran into an enigma. The “head-scratching discovery by the public consortium,” as Science termed it, was that the human genome contains 223 genes that do not have the required predecessors on the genomic evolutionary tree.
How did Man acquire such a bunch of enigmatic genes?
In the evolutionary progression from bacteria to invertebrates (such as the lineages of yeast, worms, flies or mustard weed – which have been deciphered) to vertebrates (mice, chimpanzees) and finally modern humans, these 223 genes are completely missing in the invertebrate phase. Therefore, the scientists can explain their presence in the human genome by a “rather recent” (in evolutionary time scales) “probable horizontal transfer from bacteria.”
In other words: At a relatively recent time as Evolution goes, modern humans acquired an extra 223 genes not through gradual evolution, not vertically on the Tree of Life, but horizontally, as a sideways insertion of genetic material from bacteria…
An Immense Difference
Now, at first glance it would seem that 223 genes is no big deal. In fact, while every single gene makes a great difference to every individual, 223 genes make an immense difference to a species such as ours.
The human genome is made up of about three billion neucleotides (the “letters” A-C-G-T which stand for the initials of the four nucleic acids that spell out all life on Earth); of them, just a little more than one percent are grouped into functioning genes (each gene consists of thousands of "letters"). The difference between one individual person and another amounts to about one “letter” in a thousand in the DNA “alphabet.” The difference between Man and Chimpanzee is less than one percent as genes go; and one percent of 30,000 genes is 300.
So, 223 genes is more than two thirds of the difference between me, you and a chimpanzee!
An analysis of the functions of these genes through the proteins that they spell out, conducted by the Public Consortium team and published in the journal Nature, shows that they include not only proteins involved in important physiological but also psychiatric functions. Moreover, they are responsible for important neurological enzymes that stem only from the mitochondrial portion of the DNA – the so-called “Eve” DNA that humankind inherited only through the mother-line, all the way back to a single “Eve.” That finding alone raises doubt regarding that the "bacterial insertion" explanation.
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