The real 'missing links'

Gentlemen, we think we finally found what makes you human. All this time, we (mostly us ladies) were focusing on the striking similarities between you and your other primate cousins — chimps. Can you blame us, though, when you make it so easy to compare than to contrast? But alas, science has interrupted the fun and pointed to something that you lost on the evolutionary highway we all once shared with chimps.

A group of scientists published a study in the journal Nature last March 9 entitled “Human-specific loss of regulatory DNA and the evolution of human-specific traits.” They were Cory Y. McLean, Philip L. Reno, Alex A. Pollen, Abraham I. Bassan, Terence D. Capellini, Catherine Guenther, Vahan B. Indjeian, Xinhong Lim, Douglas B. Menke, Bruce T. Schaar, Aaron M. Wenger, Gill Bejerano and David M. Kingsley. They compared the genome (the DNA map) of chimps and other mammals with that of humans. Around five to six million years ago, humans shared a common ancestor with chimps (we were not chimps, as those who do not understand “evolution” always say). This is why we share at least 96 percent of our genome with chimps. But obviously, we humans are a different species of primates. By comparing these DNA stretches, they saw that some stretches numbering around 511, we once shared with chimps have disappeared in humans.   

These DNA stretches that were missing were not the DNA that coded for genes but those that were “regulatory.” This means these DNA were the ones that Once called “junk DNA,” we know now that acted as the switches for genes, on whether they will be on or off or how they will conspire or oppose another gene/s. Only two percent of our DNA code for genes, the rest seem to act as this “bureaucracy” for processing that two percent.   

One of the missing DNA is what made human males lose their spines. I am not referring to the spines on men’s backs but to spines (more like thorns) down there — in penises. Chimps and other primates have these spines in their penises and it is known to make their sexual organs extra sensitive. This made the male release sperm quickly. They are even suspected to be able to remove sperm that is already in the female cavity. Efficiency was the battle cry of these spiny organs. These spines seemed useful in nature in the context of fierce competitions among male primates for the female. However, having lost these spines, the human male organ became less sensitive and now required a longer time to implant itself in the female domain. Scientists infer that this made for more intimate bonding and probably, a tendency away from having many partners toward monogamous relationships. Following this reasoning, a “less endowed” penis is probably one of the things that define modern human males.   

This “missing” DNA not only deleted spines in the male penis but was also responsible for a receptor that enables the bearer to grow whiskers. Whiskers are known in biology to aid in sensing danger from the environment. A presence that moves the air even slightly could be detected by whiskers. Gentlemen, you may thank or curse this missing DNA for the fact that you do not bear whiskers. For us ladies, it is one less thing for us to watch you men get worked up over, aside from cars.   

When I am asked, what is it I learned that matters to me now, I always reply that I think it is more of what I shed that helps define me. We often think that we humans are special because we have “more.” It turns out that in biology, it is what we have lost that made us who we are now. The scientists also found that one of the missing DNA switched genes to stop the production of brain cells in other mammals. Without this DNA stretch, scientists think that we humans were able to enlarge our brains, particularly the cortex, which is the main region responsible for “higher thinking” that is absent, or crudely present, in other animals. For sure, there will be more revelations to come as scientists discover what we have lost from our primate heritage and defined our biology as humans.   

Oh and if you were a male who habitually and conveniently cites your ape genetic heritage to justify your philandering, make sure you got the built-in spines to support your biological excuse. That will set you back five to six million years back but hey, a man’s gotta do what his ape cousins are armed to do, right?  

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