Mountain gorilla inbreeding has distorted their facial features

[ad_1]

The mountain gorilla population is small and inbreeding levels are high – and now there’s evidence this inbreeding may explain why some gorillas have distorted facial features



Life



23 February 2022

An extreme example of facial asymmetry in a female Virunga mountain gorilla cranium (Tayna, individual GP.148), shown as a three-dimensional surface model with texture. This individual was not included in the sample as she was dentally immature at the time of death, but she exhibits an extreme version of the asymmetric pattern documented in this study.

An extreme example of facial asymmetry in a female Virunga mountain gorilla cranium

McGrath K et al.

The degree of facial feature distortion is on the rise in certain endangered gorilla species, along with their level of inbreeding.

Facial asymmetry in primates – including humans – is marked by a sort of spiraling of the facial features around a central point just above the jaw. Once thought to be a consequence of early life challenges, a new study in gorillas suggests that the phenomenon may result from inbreeding, says Kate McGrath at the University of Bordeaux, in France.

“It’s either that inbreeding is somehow directly affecting their facial development, or that [being] inbred is making them more susceptible to … illness or other things that pop up in early life,” she says. Or it may be a combination of both factors, she adds.

Join us for a mind-blowing festival of ideas and experiences. New Scientist Live is going hybrid, with a live in-person event in Manchester, UK, that you can also enjoy from the comfort of your own home, from 12 to 14 March 2022. Find out more.

Scientists have recognised facial asymmetry – which is “like there’s a hinge on one side of the face, and compression, which twists the face” – in mountain gorillas since at least the 1970s, says McGrath. At the time, researchers assumed this developed because the animals preferred to chew on one side of the mouth.

Later, other research groups suggested that facial asymmetry might arise from difficult early life experiences, she says. But because mountain gorillas – with a population that, today, only includes 1000 individuals in two distinct groups – have such significant facial asymmetry, McGrath wondered if the trend were related instead to high levels of inbreeding.

To investigate, she and her colleagues ran 3D geometric morphometrics on the skulls of 40 Virunga mountain gorillas (Gorilla beringei beringei) and compared them to those of 40 eastern lowland, or grauer, gorillas (G. beringei graueri) and 34 western lowland gorillas (G. gorilla gorilla). All gorillas were adults and represented both males and females that had died between 1880 and 2008.

They found that the mountain gorillas had nearly twice as much facial asymmetry compared to grauer gorillas, and nearly three times as much compared to western lowland gorillas. The results line up with the level of inbreeding in each population, says McGrath, since western lowland gorillas have been the least inbred of the three subspecies over the past 130 years, and mountain gorillas are “exceptionally inbred” – more so than any other ape, including human groups like the Neanderthals that are known to have been inbred. Grauer gorillas, meanwhile, fall somewhere in the middle.

Environment did not seem connected to facial distortion, she adds. In fact, mountain gorillas live in protected natural areas with abundant grass, leaves, and shoots to eat. And as for chewing side preferences, the scientists found no links whatsoever between facial asymmetry and tooth wear, thereby overturning the 1970s hypothesis.

Primates may even have evolved to recognise facial asymmetry as a sign of a potentially unhealthy mate, says McGrath. In previous studies, both people and animals have shown more attraction to symmetrical faces. “I think it’s a really interesting possibility,” she says. “Basically, is that symmetry a sort of reliable indicator of the genetic fitness of the [individual]? I think our work supports that idea.”

Even so, when populations are small – as in the case of mountain gorillas – mate choices are limited, she says.

While mountain gorillas are the most inbred, western lowland gorillas and especially grauer gorillas have experienced dramatic drops in population levels in recent decades, mainly due to human diseases and poaching, McGrath says. This probably affects their inbreeding status – the trends of which seem to be reflected in the new study’s preliminary time-related findings.

“We see that facial symmetries are increasing in all three groups throughout time,” she says. “That fits with what we know from the genetic data, that inbreeding is an ongoing problem.”

Journal reference: Proceedings of the Royal Society B, DOI: 10.1098/rspb.2021.2564

More on these topics:

[ad_2]

Source link

Advertisement

spot_img

How to convert a...

Whether you’re more comfortable working in PowerPoint or...

When To Stop Watering...

You can stop watering new grass seed daily...

Senate Preps for Hearings...

Washington —  On Monday, the U.S. Senate Judiciary Committee...

What DisplayPort’s new Ultra-High...

The Video Electronics Standards Association (VESA) has announced...

How to convert a Word document to a PowerPoint presentation

Whether you’re more comfortable working in PowerPoint or you’d like to present the content of your Word document in a different way, we’ve...

When To Stop Watering New Grass Seed 2022

You can stop watering new grass seed daily once it has germinated and the grass blades measure to about 1 inch. This should...

Senate Preps for Hearings on Biden’s Ground-Breaking Supreme Court Pick 

Washington —  On Monday, the U.S. Senate Judiciary Committee will begin four days of hearings on the nomination of Judge Ketanji Brown Jackson to...

What DisplayPort’s new Ultra-High Bit Rate (UHBR) certification means to you

The Video Electronics Standards Association (VESA) has announced a new DisplayPort certification called Ultra-High Bit Rate (UHBR) for DisplayPort 2.0. It establishes two...

Discover the best ways to earn passive income in 2022 with this $20 bundle

If you’re trying to get rich working for someone else, then the best of luck to you. From a practical sense, the only...
Previous articleVOA Newscasts
Next articleVOA Newscasts