The general theory that humans have essentially stopped evolving has never sat well with me. For why should that be the case, what could have told our DNA to stop adapting to its situation, like it has been doing since the first strand of DNA ever evolved in the first place? From the University of Utah comes a study which not only suggests that humans are indeed still evolving, but have actually been doing so at an accelerated rate since the advent of farming and the end of the ice age some 10,000 years ago.
“We used a new genomic technology to show that humans are evolving rapidly, and that the pace of change has accelerated a lot in the last 40,000 years, especially since the end of the Ice Age roughly 10,000 years ago,” -Henry Harpending, research team leader, Professor of anthropology, University of Utah.
“Ten thousand years ago, no one on planet Earth had blue eyes, we are different from people who lived only 400 generations ago in ways that are very obvious; that you can see with your eyes.”- John Hawks team member.
Analysing the DNA of 270 people from Chinese, Japanese, African and Western European genetic heritages. Henry Harpending and his team looked specifically at the single nucleotide polymorphisms (SNP’s) which are the differences observed between two DNA sequences from members of the same species.
“If a favourable mutation appears, then the number of copies of that chromosome (with the favourable mutation) will increase rapidly. And if it increases rapidly, it becomes common in the population in a short time,” -Henry Harpending.
Chromosome’s will over time break and recombine at random positions along the DNA strand and thus creates new variants where it does so, the more broken and recombined the older that section of DNA. But if the mutation is recent then this breaking and recombination will not have occurred yet, and if it is a favourable mutation this unbroken mutation will be present in many people. In studying what amounted to 3, 9 million SNP’s between the 270 DNA candidates Henry and his team came up with some interesting observations.
Nearly 7% of human genes are undergoing recent and rapid evolution, might not sound like much but remember there is only a 5% difference between Humans and chimpanzee’s at the genetic level.
“Our study denies the widely held assumption or belief that modern humans appeared 40,000 years ago, have not changed since and that we are all pretty much the same. We show that humans are changing relatively rapidly on a scale of centuries to millennia, and that these changes are different in different continental groups.”-Henry Harpending
40,000 years ago is the point at which it is believed that most of our modern ancestors started to move out of Africa and into the other continents. 10,000 years ago marks the end of the last ice age and the beginning of the modern human population explosion. One that was directly fuelled by the advent of farming and settled populations, and has seen us grow from millions to billions. Combining this population explosion and the relative separateness of the continents until very recently and you get some recent recognisable differences that people have evolved according to their environment.
“Human races are evolving away from each other, genes are evolving fast in Europe, Asia and Africa, but almost all of these are unique to their continent of origin. We are getting less alike, not merging into a single, mixed humanity. Humans dispersed from Africa to other regions 40,000 years ago, and there has not been much flow of genes between the regions since then. We were in new environments to which we needed to adapt, and with a larger population, more mutations occurred.” -Henry Harpending
It does make you wonder at the speed of evolution which is thought by this study to be actually 100 times faster than previously believed by those who thought something was happening, as opposed to those who thought nothing had changed in 40,000 years. If you look at a common elements now present in most cities all over the world like say a Big Mac and a Coke. One can only but wonder, have we already kept and distributed a genetic mutation that improves the digestion of said food and drink? But the interesting thing would be that even if we have, that mutation would differ from continent to continent.
“If you suddenly take hunter-gatherers and give them a diet of corn, they frequently get diabetes. We’re still adapting to that. Several new genes we see spreading through the population are involved with helping us prosper with high-carbohydrate diet.” -Henry Harpending.
One example the study latched onto was the difference in genes that allowed people in Denmark and Sweden to digest milk even as adults, yet for most of Africa and China adults no longer produce the correct enzyme to do so. This reflects the importance of diet in favourable mutation distinct to environment and region, but also the speed at which this occurs. Maize is a relative newcomer to Africa yet quickly became a staple diet; it only seems likely that a favourable mutation to better digest maize will, if it hasn’t already, be preserved and quickly passed into a maize consuming society.
It is often said that the only constant in the universe is that of change itself, in the light of this study that rings true. If you look at the Genome like the wizard within each cell, or perhaps more of a sorcerers apprentice because here is a mechanism that intentionally and regularly breaks itself apart in the hopes of a favourable mutation. A case of if its not broke don’t fix it could never apply to DNA, quite the opposite it strives constantly for change and adaptation. What Henry and his team suggest is exactly that, a process of constant change, constant evolution, and all life on this earth is the embodiment of evolution in action. Our bodies do constantly strive to adapt to situation which gives whole new meaning to the way we live our lives and how that will intimately affect our all our descendants.
“We have to understand genetic change in order to understand history” -Henry Harpending.
