Big brains and spiky penises
If you stop to think about it there is an implicit assumption that evolution is intelligent. We talk about humans being â€œfurther upâ€ the family tree from our primate ancestors like gorillas, chimps, and orang-utans. The assumption is that evolutionary changes are always for the better, that the â€œfittestâ€ is selected for, and based on a new piece of research, you would have to agree with that assumption.
The research adopted a kind of reverse model; instead of looking at what gene sequences humans have that chimpanzees do not, the researchers looked for DNA sequences that are missing in humans but present in chimps. So what they were examining was the genetic material that had been shed by humans as they evolved.
They found 510 DNA sequences missing in humans but present in chimps. A lot of these sequences were in parts of the genome that did not code for genes, but the researchers noticed two gaps in particular; one that was right next to the male hormone receptor gene and the other next to the gene involved in suppressing tumours. Based on these interesting locations they decided to see what these genes would do and therefore find what it was that human beings had jettisoned on their evolutionary journey.
They found, by inserting the genes into other species, that the first DNA sequence caused the formation of hard spines on the penis and the development of sensory whiskers. In case you are wondering why penises may have developed spines in the first place, and why chimps and other species still have them, it is thought that they remove the sperm of male competitors when mating with females.
The second sequence was found to act as a brake on brain size so by removing that DNA sequence, brains were able to grow bigger.
So by dropping these two DNA sequences humans were able to develop smooth penises suited to a more monogamous, and presumably pleasant, sex life. They were also able to develop bigger brains which arguably may be less suited to monogamy, but that is a Pandoraâ€™s box for another day.