Study: Humans 'may have evolved with genes from plants'

Cambridge University research challenges popular belief about evolution

Humans may have evolved with genes acquired from plants, micro-organisms and fungi according to a new study.

The University of Cambridge findings challenge long-held perceptions about evolution and suggest that the process may be ongoing.

The findings also confirm the conclusions of a controversial 2001 study which suggested that humans may have evolved with genes acquired from plants but had much less data available to analyse. Academics widely dismissed its findings at the time and methods used.

Researchers now accept that around one per cent of the human genome could have been transferred from plants and other sources following the significantly larger study.

The mechanism by which genes spread is a process known as horizontal gene transfer (HGT), in which bacteria share genetic information.

HGT occurs in a number of ways including through the introduction of foreign genetic material and the transfer of DNA between bacteria by a virus.

However, the research suggests that this practice was much more widespread than previously thought and may have contributed to the evolution of all animals.

Researchers found that many animals, including humans, carried essential "foreign" genes from microorganisms co-habiting their environment in ancient times as opposed to genes solely passed down through ancestral lines.

Lead author Alastair Crisp, a research associate at the university's chemical engineering and biotechnology department, acknowledged that the findings would prove "somewhat controversial".

He said: "It changes how we think about the evolutionary tree. It's not just this straight-forward single branching tree like you see in your garden in which one branch leads on to another, it's more like a strangled fig in which the branches are growing into each other."

The study, published in the journal Genome Biology, is the first to show how widely horizontal gene transfer occurs in animals and suggested that it mainly originated from bacteria.

Researchers studied the genomes of 12 species of fruit fly, four species of nematode worm, and 10 species of primate, including humans.

They used compared them to the genes of hundreds of other species, working out which were aligned and then estimating how long ago they were acquired.

In humans, they identified 128 foreign genes in the human genome that had not previously been reported. The majority were related to enzymes involved in metabolism.

The gene transfer in animal species mainly originated from bacteria and protists, a class of microorganism. Others came from viruses.

Dr Crisp added: "We can now show that HGT is not just confined to micro-organisms. It has played a role in all species we looked at.

"We now need to look at evolutionary models to take this information into account.

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

He said it was not known how the transfers happened but said that it was millions of years ago and suspected to be down to "random chance".

"It's less than one per cent of the human genome that's been transferred," he added.