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Wombling Free: Genome sequencing of the Wombles reveals complex genetic history and evolution of litter picking

Earlham Institute has released a full Womble genome sequence, shedding light on the evolutionary origins of litter picking & the genetic basis of ageing.

April 01, 2018

Earlham Institute has today released a full sequence of the Womble genome, shedding light on the evolutionary origins of litter picking and the genetic basis of ageing, as well as complex genetic retroviral transmission across diverse mammal species.

Despite poor DNA samples, which were mostly obtained from abandoned burrows on Wimbledon Common, researchers applied the Womble motto “Make Good Use of Bad Rubbish” to perform the genome sequencing experiment, which used a combination of Illumina HiSeq short-reads and longer reads sequenced using nanopore technology.

The wombles were of particular interest to the team, based at Earlham Institute in Norwich, UK, due to a “sixth sense” which allows the creatures to sense green spaces and wildlife, perhaps contributing to their urge to clean up litter.

Of greater interest to scientists is how these creatures, originally thought to be relatives of burrowing mammals such as badgers, have come to adopt human-like activities such as cooking; preparing daisy buns, acorn juice, elm-bark casserole and fir cone soufflé.

Using the 13-or-so individual genome sequences obtained, which came to around 3Gb - just smaller than the human genome - a bioinformatics team led by PhD student Ben White sought to investigate the evolutionary history of the wombles, and how they came to be so environmentally conscious.

A typical scene: Wombles investigating a haul of precious litter. Credit:Flickr

Wombles at home

Remember you're a Womble.

Phylogenetic analysis showed that wombles (also previously named as Womblus commonus ssp. litterpickerus), who mostly live elusively among humans yet are thought to have a worldwide distribution, are not mustelids at all but form a sister group to the raccoons in the genus Procyon. Thus, a new scientific name for the Wombles has been proposed, Procyon wombleus.

Interestingly, however, analysis of certain genetic regions revealed a high amount of transposable genetic elements, many of which are linked to regions found within the human genome.

Dr Chris Watkins, who managed the project, said, “we’re clearly not looking at just another raccoon here. Though similarities can be drawn between the two animals, including their close proximity to human rubbish, the Wombles seem to have somehow become more human.”

Further analysis showed that these regions are almost completely absent in the closely-related raccoon, causing researchers to wonder just how these integration events may have occurred. All in all, the additional DNA incorporated from the human genome made up for an extra 0.15Gb compared to raccoons, which have a genome size of approximately 2.85Gb.

Ben White, who led the bioinformatics analysis, said, “the more we looked into the human genome, particularly thanks to the long read sequences, the more these transposable elements came into play. We think we’re looking at a rare virus that seems to have transferred some essence of humanness into the Wombles.”

The team admits that further research is necessary in order to source just how the Wombles have taken up this human DNA, but initial investigations point towards a novel type of human-derived retrovirus found in samples of litter scattered across Wimbledon Common.

Leah Catchpole, who led the DNA sequencing efforts, added, “we need better data to be sure exactly of what these integration events were, but studies into the closest relatives of the Wombles, the raccoons, suggest that this was a unique event that occurred from a single population of raccoons in Wimbledon.”

Phylogeny of the wombles, which cluster with the raccoons. Raccoon phylogeny thanks to Koepfli et al. 2006.

Womble family tree

Retro raccoons.

The team suggests that the Womble is almost entirely derived from a population of raccoons that was known to live in and around Wimbledon Common after being released by a group of raccoon enthusiasts in the Victorian era.

Genome sequencing of one of the raccoon samples, found pickled in the Natural History Museum, showed that these animals are essentially direct relatives of the Wombles sequenced on Wimbledon common, with one of 13 Womble genomes sampled shown to be a cousin of the raccoon.

It is thought that a retroviral insertion event led to the wombles developing their surprisingly human characteristics, highlighted recently by the discovery of an atlas at the front of one of the disused burrows on Wimbledon Common, along with various copies of the Times and mounds of litter, from which the retrovirus particles were isolated.

The team is now investigating the genetic elements that may be associated with litter picking, hoping to find more burrows in the future that do not have such an abundance of human leftovers, so as to perform a genetic comparison.

Open quote marks

Well my Womble didn’t live ‘til 157, he fell apart after a few years. But he did get lots of love.

Closing quote marks

Credit: Adam Dobias/Shutterstock.com

You and I are gonna Womble forever.

Another interesting angle that the team is looking to investigate in the future is the apparent longevity of the Wombles, based on analysis of whole chromosomes derived from the genome sequencing efforts. Telomere analysis showed the caps of Womble chromosomes to be significantly larger than those of humans or raccoons, while telomere degradation showed several of the Womble individuals to be approximately 157 years old.

Some people were less enthusiastic about the outcomes of the research study. Sasha Stanbridge said, “well my Womble didn’t live ‘til 157, he fell apart after a few years. But he did get lots of love.”

There is clearly much yet to be discovered about the reclusive Wombles, but what is for sure is that, lest you forget, as Ben reminds us: “remember-member-member what a Womble Womble Womble you are.”

The Wombles are fictional pointy-nosed, furry creatures created by author Elisabeth Beresford, originally appearing in a series of children's novels from 1968.

Article author

Peter Bickerton

Scientific Communications & Outreach Manager

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