In a year that celebrates the 200th anniversary of the birth of Darwin and the 150th anniversary of the publication of “On the Origin of the Species”, scientists from Murdoch University in Australia have made an exciting discovery. Their hypothesis, which argues that DNA junk is essential for evolution, may represent one of the biggest advances in evolutionary theory, since the 1930s.

Murdoch University scientists have developed an improved theory of evolution – a groundbreaking hypothesis which finally reconciles evolutionary theory with the fossil record.

Developed by PhD student Keith Oliver and Program Chair of Biomedical Sciences Dr Wayne Greene, the “Genomic Drive” hypothesis, potentially represents one of the biggest advances in evolutionary theory since the 1930s.

DNA “junk”

In a co-authored report, due to be published in the prestigious BioEssays journal, the researchers argue that transposable elements (TEs) – or what is colloquially termed jumping genes, selfish or junk DNA, have a critical role in ensuring the survival of biological lineages.

Without this DNA junk, a species is effectively frozen and faces eventual extinction.

On the other hand, species with genomes with high TE activity or strong presence of identical TEs possess a greater ability to evolve, diversify and survive.

Take for example humans, rodents and bats.

As primates some 46 per cent of the human genome is comprised of TEs while other mammals such as rodents and bats are known to possess around 40 per cent.

These TE’s are generally suppressed in the ordinary body cells of most species but are allowed to reactivate in reproductive cells for the potential benefit of the next generation.

Their activity can also be triggered when they suddenly hop between species or by stress.

TEs do their survival work by reformatting and rearranging DNA genomes to sometimes create significant adaptive mutations that undergo natural selection.

Species without junk DNA risked extinction

Dr Greene said species that were devoid of TEs were more at risk of extinction because they simply lacked the capacity to adapt, change and diversify.

“If you don’t have this junk in your genome then you can’t evolve and are stuck, thereby remaining in what is termed evolutionary stasis,” Dr Greene said.

“This would explain why almost all species control their TEs rather than eliminate them.

“And of course having these TEs in a genome doesn’t mean a lineage will necessarily diversify. What it does mean is that it has a much greater potential to do so.”

Mr Oliver said an example of evolutionary stasis occurring in species without TE activity could be seen in the living fossil, the coelacanth, once thought to be extinct for 63 million years.

The coelacanth, which had been found off the coast of South Africa and Indonesia, had inactive or low levels of TEs and had been in stasis for 400 million years.

In another example he referred to the tuatara, where just two species had been found off the coast of New Zealand.

Like the coelacanth, the tuatara was characterised by very few jumping genes and has been unchanged for 220 million years.

An explanation for many unanswered questions

Dr Greene said Genomic Drive theory provided an explanation for many unanswered questions such as why species suddenly appeared in the fossil record, why some groups of organisms were species rich and others species poor and why some species changed little over millions of years.

Successive waves of TE activity in a lineage potentially explained alternations of rapid evolution and stasis.

He said some species – such as bats which “came out of nowhere” in the Eocene Period – suddenly appeared in the fossil record.

This was in keeping with evidence that TE or jumping gene activity occurred in sudden episodic bursts.

Credited to www.sciencealert.com.au
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