1. Evolution and genome analysis

“We’re trying to get a more unified view of natural selection as seen from the National Geographic reports and what we see in genetics,” explained Jaume Bertranpetit. To do so, laboratories all over the world are comparing millions and millions of pieces of data: they’re looking for changes in the DNA sequence that are consistently different among today’s populations and/or they are comparing our genetic information with that of our ancestors. Then they try to establish what has caused these changes, an advantage or simply chance: they are trying to figure out whether they were selected. And, if they were, why.

There are many changes that could take place and they aren’t always easy to identify. Sometimes they are specific mutations, changes in a single gene that are beneficial depending on the context. This is what has allowed most of the modern population to continue drinking milk without problems throughout their lives: 10,000 years ago, one single genetic mutation (although it could have been several) allowed the body to manufacture lactase –the protein that allows us to digest milk-  throughout life and not just as infants (as is common in nature). The advantage was important, taking into account that humans had already began raising livestock, and the mutation was selected in the European population to such an extent that between 60% and 90% of the European population now carries this mutation.

Sometimes, however, the mutations affect multiple genes, and it is the sum of their effects that accounts for the final result. This tends to be more complicated to study, and is what happens with the change of skin tone. As humans moved away from the equator and were exposed to less sunlight, their skin became lighter, very possibly to make the most of the available sun and continue producing vitamin D, which in generally very scarce in our diet.

On other occasions, the genetic “novelties” are “borrowed” from other species. Some of our genes come from cross-breeding with other archaic humans such as Neanderthals or Denisovans. This is known as introgression.

There are many mechanisms, and it is difficult to establish whether the results are truly due to natural selection. For Aida Andrés, researcher at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, “It is clear that we have adapted to new environments since humans left Africa, although diversity is very limited overall.” Elena Bosch suggests the possibility that “Perhaps selection is there but we don’t have the means to identify the changes or explain them.” And she adds, “If we take into account all the laboratories working on this topic and the number of genes sequenced, we’re not having much success. But each sign is fascinating and fantastic.”