In a recent study published in Genome Biology, scientists at University of Cambridge showed that the human genome is not fully human. The scientists studied the genome of forty species, of which ten were primates, including humans. In the study they identified 145 “foreign” genes in the human genome that have its origins from other species, mainly bacteria and protists. The process of gene transfer between species is known as horizontal gene transfer (HGT). It is already known that HGT occurs in simple organisms like bacteria. Bacteria that are resistant to antibiotics for example can transfer their antibiotic resistant gene to non-resistant bacteria and make them antibiotic resistant. A more extreme example is the bacterium Wolbachia, which can transfer its entire genome into the fruit fly Drosophila ananassae. Although these examples are well known, less is known about HGT in more complex organisms like humans. Of the 145 foreign genes that were identified in the human genome, the majority of them are involved in metabolic processes. This suggests that HGT contributes to diversify human cells and make them capable to perform advanced biochemical processes that are not possible in bacteria.
The study also showed that HGT in humans have occurred throughout evolution and is still ongoing. I find this very interesting because this means that the phylogenetic tree of life with clear separate branches, which we are used to see it as, is actually more complex with connections between branches.
I don’t want to sound too cheesy, but this study shows how awesome nature is.