Subscribe to our free daily newsletters
. Earth Science News .




Subscribe to our free daily newsletters



ABOUT US
Inbred Neanderthals left humans a genetic burden
by Staff Writers
Washington DC (SPX) Jun 07, 2016


The results suggest that Neanderthals carried many mutations with mild, but harmful effects. The combined effect of these weak mutations would have made Neanderthals at least 40% less fit than humans in evolutionary terms - that is, they were 40% less likely to reproduce and pass on their genes to the next generation.

The Neanderthal genome included harmful mutations that made the hominids around 40% less reproductively fit than modern humans, according to estimates published in the latest issue of the journal GENETICS. Non-African humans inherited some of this genetic burden when they interbred with Neanderthals, though much of it has been lost over time.

The results suggest that these harmful gene variants continue to reduce the fitness of some populations today. The study also has implications for management of endangered species.

"Neanderthals are fascinating to geneticists because they provide an opportunity to study what happens when two groups of humans evolve independently for a long time - and then come back together," says study leader Kelley Harris, of Stanford University. "Our results suggest that inheriting Neanderthal DNA came at a cost."

Previous studies of DNA extracted from Neanderthal remains revealed that these Eurasian hominids were much more inbred and less genetically diverse than modern humans. For thousands of years, the Neanderthal population size remained small, and mating among close relatives seems to have been common.

Then, 50,000-100,000 years ago, groups of anatomically modern humans left Africa and moved to the homelands of their distant Neanderthal cousins. The two groups interbred, mingling their previously distinct genomes. But though a small fraction of the genome of non-African populations today is Neanderthal, their genetic contribution is uneven. Neanderthal sequences are concentrated in certain parts of the human genome, but missing from other regions.

"Whenever geneticists find a non-random arrangement like that, we look for the evolutionary forces that caused it," says Harris.

Harris and her colleague Rasmus Nielsen (University of California, Berkeley / University of Copenhagen) hypothesized that the force in question was natural selection. In small populations, like the Neanderthals', natural selection is less effective and chance has an outsized influence. This allows weakly harmful mutations to persist, rather than being weeded out over the generations. But once such mutations are introduced back into a larger population, such as modern humans, they would be exposed to the surveillance of natural selection and eventually lost.

To quantify this effect, Harris and Nielsen used computer programs to simulate mutation accumulation during Neanderthal evolution and to estimate how humans were affected by the influx of neanderthal genetic variants. The simulations incorporated data on the mutation rates, genome properties, and population dynamics of hominids.

The results suggest that Neanderthals carried many mutations with mild, but harmful effects. The combined effect of these weak mutations would have made Neanderthals at least 40% less fit than humans in evolutionary terms - that is, they were 40% less likely to reproduce and pass on their genes to the next generation.

Related conclusions were reached in an independent study that used very different methods, led by Ivan Juric at the University of California, Davis. This work is currently being peer reviewed and is available at the pre-publication preprint server bioRxiv.

Harris and Nielsen's simulations also suggest that humans and Neanderthals mixed much more freely than originally thought. Today, Neanderthal sequences make up approximately 2% of the genome in people from non-African populations. But Harris and Nielsen estimate that at the time of interbreeding, closer to 10% of the human migrants' genome would have been Neanderthal. Because there were around ten times more humans than Neanderthals, this number is consistent with the two groups acting as as single population that interbred at random. Recent DNA evidence has confirmed that the Neanderthal contribution to Eurasian genomes was higher in the past.

Although most of the harmful mutations bequeathed by our Neanderthal ancestors would have been lost within a few generations, a small fraction likely persists in people today. Harris and Nielsen estimate that non-Africans may have historically had approximately 1% lower reproductive fitness due to their Neanderthal heritage. This is in spite of the small number of Neanderthal gene variants thought to be beneficial today, including genes related to immunity and skin color.

The results also have implications for conserving endangered species. Many vulnerable populations in fragmented habitats face similar genetic problems to the Neanderthals: inbreeding, low genetic diversity, and accumulation of harmful mutations. One management strategy for overcoming these problems is genetic rescue - improving the health of an inbred population by outcrossing it with other populations.

"Genetic rescue is designed to move gene variants from an outbred population to an inbred population," says Harris. "Our results suggest managers must ensure that this movement only goes one way; otherwise harmful mutations from the inbred population may lower the fitness of the outbred group."


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only

.


Related Links
Genetics Society of America
All About Human Beings and How We Got To Be Here






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

Previous Report
ABOUT US
Dogs were domesticated not once, but twice
Oxford UK (SPX) Jun 03, 2016
The question, 'Where do domestic dogs come from?', has vexed scholars for a very long time. Some argue that humans first domesticated wolves in Europe, while others claim this happened in Central Asia or China. A new paper, published in Science, suggests that all these claims may be right. Supported by funding from the European Research Council and the Natural Environment Research Council, ... read more


ABOUT US
Thousands flee Sri Lanka ammunition depot explosions

Sri Lankan monks hold prayers for buried landslide victims

Ecuador needs $3.3 bn to rebuild from quake: government

Signals detected from EgyptAir black box

ABOUT US
Calculating the mechanics of a rough sphere

Microsoft wants Windows to open into mixed reality

Believe the hype? How virtual reality could change your life

Mantis shrimp inspires next generation of ultra-strong materials

ABOUT US
To fight lionfish invasion, Cuba learns to cook them

Water yields from southern Appalachian watersheds in decline since the 1970s

Hydropower dams worldwide cause continued species extinction

World's first grid-connected tidal array almost complete

ABOUT US
Nepal seeks to drain giant glacial lake near Everest

Antarctic coastline images reveal 4 decades of ice loss to ocean

USGS assesses carbon potential of Alaska lands

Bee populations expanded during global warming after the last Ice Age

ABOUT US
Study links irrigation to inaccurate climate perception

EU proposes temporary approval of weedkiller glyphosate

Ecologists advise an increase in prescribed grassland burning to maintain ecosystem

Honeybees pick up pesticides from non-crop plants, too

ABOUT US
Scientists gain supervolcano insights from Wyoming granite

Paris floods ease but alerts in France's north

France and Germany battle deadly floods

Paris museums on alert as flood chaos hits France, Germany

ABOUT US
Chinese UN peacekeeper, 3 civilians die in Mali attacks

Things will get bloody, Nigerian militant group says

DR Congo denies getting pistols from North Korea

Senegal's child beggars show limits of 'apptivism'

ABOUT US
Dogs were domesticated not once, but twice

Study: Neanderthals occupied caves earlier than thought

Space-age exploration for pre-historic bones

Remains of rice and mung beans help solve a Madagascan mystery




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News






The content herein, unless otherwise known to be public domain, are Copyright 1995-2017 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement