Humans Have Less Retrovirus Remnants in Genome, may be Linked to Developing Tool Use

Humans have fewer remnants of viral DNA in their genes compared to other mammals, a new study has found. This decrease could be because of reduced exposure to blood-borne viruses as humans evolved to use tools rather than biting during violent conflict and the hunting of animals.

Despite natural defence systems, a retrovirus occasionally infects a mammal's egg or sperm, and the virus's genetic code gets incorporated into the animal's own genome. This viral 'fossil' then passes down from generation to generation: we all carry remnants of DNA from viruses that infected our ancestors millions of years ago. These 'endogenous retroviruses' (ERVs) appear not to cause us any harm, even though they are known to result in diseases such as cancer in other animals.

A team of researchers from the University of Oxford and Plymouth University, UK, and the Aaron Diamond AIDS Research Center, USA, wondered if there was a combination of factors unique to humans that explained why these viral fossils in our genomes remain benign. They counted the number of times that retroviruses appear to have been integrated into an animal's genome in humans, comparing humans with 39 other mammalian species, including chimpanzees, dolphins and giant pandas.

Reporting their results in the journal Retrovirology, the researchers compared the genetic signature of the two edges of the virus. These edges are identical when the virus first invades the genome, but as they acquire random mutations over time, they slowly begin to diverge. By tracking this divergence, the research team could measure how long the retrovirus had spent in an animal's genome.

Using this measure, they found that, compared to other animals, far fewer retroviruses were incorporated into the genome for humans and other apes over the last 10 million years. Even compared to animals very similar to us, humans are unusual in not having acquired any new types of retroviruses into their DNA over the last 30 million years.

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Javelins From 80,000 Years Before Oldest Homo sapiens Fossil: Modern Humans Older or Not First Spear Chuckers?

The oldest known stone-tipped projectiles have been discovered in Ethiopia. The javelins are roughly 280,000 years old and predate the earliest known fossils of our species, Homo sapiens, by about 80,000 years.

These javelins are some 200,000 years older than previous examples of similar weapons, suggesting that modern humans and their extinct relatives had the know-how to create these sorts of complex thrown projectiles much earlier than often thought.

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The Spears of South Africa...from 500,000 Years ago

A University of Toronto-led team of anthropologists has found evidence that human ancestors used stone-tipped weapons for hunting 500,000 years ago – 200,000 years earlier than previously thought.

"This changes the way we think about early human adaptations and capacities before the origin of our own species," says Jayne Wilkins, a PhD candidate in the Department of Anthropology at the University of Toronto and lead author of a new study in Science. "Although both Neandertals and humans used stone-tipped spears, this is the first evidence that the technology originated prior to or near the divergence of these two species," says Wilkins.

Attaching stone points to spears – known as 'hafting' – was an important advance in hunting weaponry for early humans. Hafted tools require more effort and foreplanning to manufacture, but a sharp stone point on the end of a spear can increase its killing power.

Hafted spear tips are common in Stone Age archaeological sites after 300,000 years ago. This new study shows that they were also used in the early Middle Pleistocene, a period associated with Homo heidelbergensis and the last common ancestor of Neandertals and modern humans.

"It now looks like some of the traits that we associate with modern humans and our nearest relatives can be traced further back in our lineage", Wilkins says.

Homo erectus or Homo heidelbergensis with spears. AWESOME.