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February 7, 2014 6:46 pm
Palaeontologists studying the origins of humanity are entering a golden age of research, in which archaeological evidence is supplemented by a sudden influx of genetic information obtained by reading traces of DNA extracted from ancient bones and teeth.
Two papers published last week, one in Nature and another in Science, analyse the contribution made by Neanderthals to the modern human genome, using DNA data obtained by Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology from various Neanderthal bones.
People with non-African ancestry derive 1 to 3 per cent of their genome from Neanderthals through interbreeding on a limited scale between 40,000 and 80,000 years ago. As bands of Homo sapiens moved out of Africa and through Europe and Asia, they met Neanderthals whose ancestors had been living and evolving there for several hundred thousand years. (Neanderthals died out about 30,000 years ago.)
Although there may have been relatively few sexual encounters between Homo sapiens and Homo neanderthalensis, some Neanderthal genes conferred competitive advantage, which meant that they spread through the modern human population. This Neanderthal legacy does not exist among Africans.
The latest studies show that altogether about 20 per cent of the original Neanderthal genome lives on, though any one individual today will have a much lower proportion in his or her own genome – typically slightly more than 1 per cent.
The modern human genome is particularly rich in Neanderthal genes affecting skin and hair – suggesting that Neanderthals were better adapted to the climate than more recent arrivals. Neanderthal keratin genes, for example, may have provided better protection in more northern latitudes, says David Reich of Harvard University, who led one study.
But Neanderthal genes have also made an unexpected and unwelcome contribution to some modern diseases, especially those linked to the immune system such as Crohn’s disease and lupus, and to some types of addictive behaviour.
Although the two human species, which diverged about 500,000 years ago, obviously produced offspring when they mated, the genetic evidence suggests that these hybrids were not as fertile as the pure species. As a result, Neanderthal DNA disappeared from the parts of the modern genome concerned with sexual reproduction.
This sort of DNA-based analysis is still in its infancy, and we can expect many more revelations about the genetic contributions made to modern humanity not only by Neanderthals but also by Denisovans, another ancient human group, which left its mark particularly in east Asia.
Blue eyes, dark skin: meet the ancestors
The genome of a man who lived in Spain 7,000 years ago reveals that European hunter-gatherers had dark skin and blue eyes, according to research from the Spanish National Research Council, writes Sarah Spickernell.
Remains of the ancient human, named La Braña 1 (in an artist’s impression), were discovered eight years ago in a cave near what is now the town of León. The cold, mountainous conditions of the cave have left the DNA extremely well preserved. He is the first European hunter-gatherer to have had his genome decoded.
The results of the study, published in Nature, indicate that Europeans used to have much darker skin than they do today.
“This individual possessed African versions of the genes that determine the light pigmentation of the current Europeans, indicating that he had dark skin,” says lead researcher Carles Lalueza-Fox.
But he also possessed the same genetic variations that produce blue eyes in today’s Europeans, and the study showed that his closest present-day relatives live in northern Europe, for example in Sweden or Finland.
A second individual, La Braña 2, was also found at the site. Iñigo Olalde, lead author of the study, hopes that sequencing his DNA will reveal even more about the characteristics of these ancient people.
“The intention of the team is to try to recover the genome of the second individual, which is worse preserved, in order to keep obtaining information about the genetic characteristics of these early Europeans,” he says.
Low-cost skin patches will monitor health
Remote monitoring of patients’ health has taken another step towards a potential mass market with the development of an electronic skin patch that could be produced in many millions at a cost of less than 50 cents each (30p).
The patch was developed by PA Consulting, which advises clients as well as developing technologies alongside them. The product is intended for commercialisation in the near future by unnamed clients in the pharmaceutical and medical devices industries.
Although there is a lot of competition in the sector, Frazer Bennett, project leader, says, “No one else has built a system that can be manufactured so inexpensively on a scale of 200 million patches a year.”
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The PA patch contains a monitor, battery and low-power radio transmitter, which sends readings to a more powerful wristwatch transmitter and then on to the patient’s doctor or carer.
This system can measure heartbeat, body temperature, blood oxygen level, lung function – and whether the patient is taking their medication.
Bennett says PA is collaborating with four companies for different applications, with pharmaceutical adherence and lung function likely to be first to market. In the longer term, there is potential for using similar sensors in sports or in monitoring workers in dangerous jobs such as mining or firefighting.
The mating dilemma: fight or be fertile
The mating season is almost upon us but what approach should a male take to gain access to the best – and most – females? Should he invest more in fighting ability or in high fertility, asks Sarah Spickernell.
It depends on the species, say researchers from the University of Manchester and Syracuse University in New York, and it comes down to ensuring continued mating rights with the females.
For some species, such as the elephant seal and red deer, it’s all about being macho, because if a male has successfully fought off his competitors, he has a monopoly over the females. At the other end of the spectrum are those who invest only in having high fertility and lose no resources in being more powerful than their competitors, such as the arctic fur seal.
“We know animals try to get females in a couple of ways,” says John Fitzpatrick, lead researcher of the study, published in Nature Communications. “When they fight for them they sometimes evolve weaponry – such as antlers or a really big body size or big teeth. The other way they do this is not to bother to compete before they mate but to have big testes and the highest sperm quality so that they can fertilise the most eggs.”
Then there are those that do both, such as pheasants, minnows and bush crickets. According to Stefan Lüpold from Syracuse University, this is surprising from an evolutionary point of view.
“It is quite costly to invest in everything. You don’t get something for nothing in evolution. Some of these species invest in both, and that is a bit of a mystery.”
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