Human beings’ ancestors have routinely stolen genes from other species

http://www.economist.com/news/science-and-technology/21646197-human-beings-ancestors-have-routinely-stolen-genes-other-species-genetically

Alastair Crisp and Chiara Boschetti of Cambridge University, and their colleagues, have been investigating the matter. Their results, just published in Genome Biology, suggest human beings have at least 145 genes picked up from other species by their forebears. Admittedly, that is less than 1% of the 20,000 or so humans have in total. But it might surprise many people that they are even to a small degree part bacterium, part fungus and part alga.

Dr Crisp and Dr Boschetti came to this conclusion by looking at the ever-growing public databases of genetic information now available. They did not study humans alone. They looked at nine other primate species, and also 12 types of fruit fly and four nematode worms. Flies and worms are among geneticists’ favourite animals, so lots of data have been collected on them. The results from all three groups suggest natural transgenics is ubiquitous.

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For every transcribed messenger, they searched the world’s databases, looking for matches. They excluded the immediate relatives of each of their three groups of animals (that is, no arthropods were compared with the flies, no vertebrates with the primates and no other nematodes with the worms). They then asked whether similar-looking genes to those in a transcriptome were found more often in other animals, or in non-animals. If the former, the most likely explanation would be that they were there by common descent from animal ancestors. If the latter, then, a horizontal gene transfer from species to species seemed the most probable explanation. On average, worms had 173 horizontally transferred genes, flies had 40 and primates had 109. Humans thus had more than the primate mean.

Many of the matches are to genes of unknown purpose—for it is still the case, more than a decade after the end of the human genome project, that the jobs of many genes remain obscure. But some human transgenes are surprisingly familiar. The ABO antigen system, which defines basic blood groups for transfusion purposes, looks bacterial. The fat-mass and obesity-associated gene, the effect of which is encapsulated in its rather long-winded name, seems to come from marine algae. And a group of genes involved in the synthesis of hyaluronic acid originates from fungi. Hyaluronic acid is a chemical that is an important part of the glue which holds cells together. (It is also a frequent ingredient of skin creams.)