Experts have found that the human genetic code shares genes with hundreds of other species, including animals, plants, and fungi.
In fact, this widespread transferring of genes from one species to another has been seen to be quite common in the animal and plant kingdoms, according to researchers from the University of Adelaide in Australia.
These so-called jumping genes, called retrotransposons, played a significant role in the evolution of mammals as well as other species.
What Are Jumping Genes?
Most of the time, genes are transferred from parent to offspring through the process of reproduction. There are, however, instances when genes copy and paste themselves throughout a genome and in the genomes of other species.
"This process is called horizontal transfer, differing from the normal parent-offspring transfer," explains project leader David Adelson, director of the Bioinformatics Hub at the University of Adelaide, "and it's had an enormous impact on mammalian evolution."
For example, 25 percent of the genome of cows and sheep are made of genes that were passed on to them by other species. Jumping genes are also common in bacteria, where they are needed to help microbes develop resistance against antibiotics.
The jumping gene acts like a parasite moving from host to host, says Adelson. What is inside the DNA does not matter so much. What matters is it disrupts the species' genome and how genes are regulated.
Experts have yet to discover the specific mechanism by which genes transfer from one species to another, although they suspect that insects such as ticks, bugs, and leeches could be involved.
Largest Jumping Genes Study
In the largest study yet of jumping genes, a team of researchers in Australia has examined millions of genetic sequences collected from more than 750 species of animals, plants, and fungi.
"Most studies have only looked at a handful of species and found no evidence of transfer," says study lead author Atma Ivancevic of the University of Adelaide's Medical School. "We looked at as many species as we could."
Of specific interest were two genes, namely LINE-1 (L1) and Bovine-B (BovB). The researchers found that L1 is particularly widespread among many species. Almost all animals, including humans, were found to have the L1 gene.
The only exceptions were the monotremes platypus and echidna, suggesting that L1 jumped into the evolutionary tree after egg-laying mammals split off the main branch.
In humans, the L1 gene is associated with cancer and neurological disorders. The researchers believe that studying how this gene transfers to other species could help medical experts understand the evolution of human diseases.
Cows, Marsupials, And Frogs Have Something In Common
The second gene is BovB, a much younger gene found in cows. Earlier work done by Adelson shows BovB has made its way across an array of unrelated species, including elephants, marsupials, and reptiles. It is believed that BovB got passed around through ticks.
In the new research published in the journal Genome Biology, the team has found that BovB has also transferred at least twice to bats and frogs. It is also possible that bedbugs, leeches, and locusts also played a role in transferring this gene to other species.
In the future, the researchers plan to investigate insects to see if they can find more genes shared across a wider set of species. They are also looking into the possible role that sea worms and nematodes may have played in the horizontal transfer of genes.