Humans may have evolved with the genes of plants, fungi and micro-organisms, according to a consensus-challenging Cambridge University study.

The study into the literal roots of mankind builds on, and to some extent confirms, the findings of a 2001 investigation into whether or not humans could have acquired DNA from plants.

It was heavily criticized at the time for being too weedy.

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It is now accepted in some quarters that up to one percent of our genome could have originated in plants by way of horizontal genetic transfer, or HGT, a complex process in which particular bacteria transfer information about DNA.

The research suggests that humans, like certain other species, carried the DNA of organisms which lived in their surrounding environment rather than obtaining it through the much more linear process of breeding and descent.

In a statement on the University of Cambridge website, Dr. Alistair Crisp, lead author of the project undertaken by the Department of Chemical Engineering and Biotechnology, said: “This is the first study to show how widely horizontal gene transfer occurs in animals, including humans, giving rise to tens or hundreds of active 'foreign' genes.”

“Surprisingly, far from being a rare occurrence, it appears that this has contributed to the evolution of many, perhaps all, animals and that the process is ongoing. We may need to re-evaluate how we think about evolution.”

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In an article for the Genome Biology journal published Friday, the authors of the report further explained: “HGT occurs at low, but appreciable, levels across all the animal species we examined; it has occurred over time and is still occurring; it mainly originates from bacteria and protists; and the genes concerned frequently code for enzyme activities.”

“Interestingly, overall levels of HGT do not appear to be conspicuously different in vertebrates and invertebrates. This is surprising given the difference in complexity between the groups, but may be explained by the observed older HGT in primates, suggesting that the vertebrate HGT may have occurred at an earlier stage of vertebrate evolution.”