Humans and Neandertals interbred, new method confirms
Technical objections to the idea that Neandertals interbred with the ancestors of Eurasians have been overcome, thanks to a new genome analysis method. The technique can more confidently detect the genetic signatures of interbreeding than previous approaches and will be useful for evolutionary studies of other ancient or rare DNA samples.
A new genome analysis method
confirms that Neandertals
with the ancestors of Eurasians.
echnical objections to the idea that Neandertals interbred with the ancestors of Eurasians have been overcome, thanks to a genome analysis method described in the April 2014 issue of the journal Genetics. The technique can more confidently detect the genetic signatures of interbreeding than previous approaches and will be useful for evolutionary studies of other ancient or rare DNA samples.
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Bacteria Could Grow Futuristic ‘Self-Healing’ Materials
by Katia Moskvitch posted on April 05, 2014 04:37PM GMT
Why bother to manufacture materials if you can grow them organically?
From athletes to couch potatoes: Humans through 6,000 years of farming
Research into the strength and shape of lower limb bones shows that, in the first 6,000 years of farming, our ancestors in Central Europe became less active as their tasks diversified and technology improved. Anthropologists show that this drop in mobility was particularly marked in men.
Early Neolithic 35-40 year old male
from Vedrovice, Czech Republic.
Human bones are remarkably plastic and respond surprisingly quickly to change. Put under stress through physical exertion — such as long-distance walking or running — they gain in strength as the fibres are added or redistributed according to where strains are highest. The ability of bone to adapt to loading is shown by analysis of the skeletons of modern athletes, whose bones show remarkably rapid adaptation to both the intensity and direction of strains.
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Why did humans replace Neanderthals? Paleo diet didn’t change, the climate did
Why were Neanderthals replaced by anatomically modern humans around 40,000 years ago? One popular hypothesis states that a broader dietary spectrum of modern humans gave them a competitive advantage on Neanderthals. Geochemical analyses of fossil bones seemed to confirm this dietary difference. Indeed, higher amounts of nitrogen heavy isotopes were found in the bones of modern humans compared to those of Neanderthals. However, these studies did not look at possible isotopic variation of nitrogen isotopes in the food resource themselves. In fact, environmental factors such as aridity can increase the heavy nitrogen isotope amount in plants, leading to higher nitrogen isotopic values in herbivores and their predators even without a change of subsistence strategy.
hy were Neanderthals replaced by anatomically modern humans around 40,000 years ago? One popular hypothesis states that a broader dietary spectrum of modern humans gave them a competitive advantage on Neanderthals. Geochemical analyses of fossil bones seemed to confirm this dietary difference. Indeed, higher amounts of nitrogen heavy isotopes were found in the bones of modern humans compared to those of Neanderthals, suggesting at first that modern humans included fish in their diet while Neanderthals were focused on the meat of terrestrial large game, such as mammoth and bison.
However, these studies did not look at possible isotopic variation of nitrogen isotopes in the food resource themselves. In fact, environmental factors such as aridity can increase the heavy nitrogen isotope amount in plants, leading to higher nitrogen isotopic values in herbivores and their predators even without a change of subsistence strategy. A recent study published in Journal of Human Evolution by researchers from the University of Tübingen (Germany) and the Musée national de Préhistoire in Les Eyzies-de-Tayac (France) revealed that the nitrogen isotopic content of animal bones, both herbivores, such as reindeer, red deer, horse and bison, and carnivores such as wolves, changed dramatically at the time of first occurrence of modern humans in southwestern France.
The changes are very similar to those seen in human fossils during the same period, showing that there was not necessarily a change in diet between Neanderthals and modern humans, but rather a change in environment that was responsible for a different isotopic signature of the same food resources.
Moreover, this isotopic event coinciding in timing with the replacement of Neanderthals by modern humans may indicate that environmental changes, such as an increase of aridity, could have helped modern humans to overcome the Neanderthals.
These new results, together with recently published research showing that Neanderthals had more skills and exploited more diverse food resources than previously thought, makes the biological differences between these two types of prehistoric humans always smaller. In this context, the exact circumstances of the extinction of Neanderthals by modern humans remain unclear and they are probably more complex than just a behavioral superiority of one type of humans compared to the other.
The Trouble with Darwin
Like many others, I watched the recent debate between Bill Nye and Ken Ham with a queer mixture of awe and déjà vu. Who knew that 89 years later, we’d still be litigating the Scopes trial? As someone trained in the sciences, I find it horrifying that there are college-educated people in the U.S. (and around the world) who believe the earth is 6,000 years old; and yet at the same time, I have a certain amount of discomfort, myself, with evolutionary theory—not because it demeans the nobility of man or denies the Bible, or anything of that sort, but because it’s such an incomplete and unsatisfying theory on purely scientific grounds. (Many physicists feel much the same way about quantum theory.)
It always amazes me that creationists do so litte research on Darwinism before attacking it. Darwin’s theory is subject to some very legitimate scientific criticisms. Biologists are, by and large, painfully aware of the theory’s shortcomings.
Darwin’s landmark work was called The Origin of Species, yet it doesn’t actually explain in detail how speciation happens (and in fact, no one has seen it happen in the laboratory, unless you want to count plant hybridization or certain breeding anomalies in fruit flies). Almost everything in evolutionary theory is based on “survival of the fittest,” a tautology that explains nothing. (“Fittest” means most able to survive. Survival of the fittest means survival of those who survive.) The means by which new survival skills emerge is, at best, murky. Of course, we can’t expect Darwin himself to have proposed detailed genetic or epigenetic causes for speciation, given that he was unaware of the work of Mendel, but the fact is, even today we have a hard time figuring out how things like a bacterial flagellum first appeared.
When I was in school, we were taught that mutations in DNA are the driving force behind evolution, an idea that is now thoroughly discredited. The overwhelming majority of non-neutral mutations are deleterious (reducing, not increasing, survival). This is easily demonstrated in the lab. Most mutations lead to loss of function, not gain of function. Evolutionary theory, it turns out, is great at explaining things like the loss of eyesight, over time, by cave-dwelling creatures. It’s terrible at explaining gain of function.
It’s also terrible at explaining the speed at which speciation occurs. (Of course, The Origin of Species is entirely silent on the subject of how life arose from abiotic conditions in the first place.) It doesn’t explain the Cambrian Explosion, for example, or the sudden appearance of intelligence in hominids, or the rapid recovery (and net expansion) of the biosphere in the wake of at least five super-massive extinction events in the most recent 15% of Earth’s existence.
Of course, the fact that classical evolutionary theory doesn’t explain these sorts of things doesn’t mean we should abandon the entire theory. There’s a difference between a theory being wrong and being incomplete. In science, we cling to incomplete theories all the time. Especially when the alternative is complete ignorance.