#naturalselection

#naturalselection

Why Do Humans Sleep Less than Other Primates?Adult humans average about seven hours of sleep per day. By contrast, chimpanzee, one of our closest relatives, sleep 9.5 hours a day, and other primates sleep even longer. Why is that? Common sense might tell you that it's because of television, the internet, stress, artificial schedules, and lights. But studies show that non-industrial communities, even those without electricity, sleep about the same amount. There's something about being human that causes us to get less sleep than other primates. Some new studies give us a hypothesis and some caveats. It's possible that we evolved to operate on less sleep when we stopped living in trees. Animals that sleep on the ground are at a higher risk from predators, so our ancestors began sleeping in groups with someone keeping watch in shifts. That would also explain why humans have more flexible sleep patterns than other primates. The caveat is that we might not know as much about animal sleep patterns as we think we do. Some studies show that creatures who live in zoos and laboratories sleep more than those in the wild, although studies of how long wild animals sleep in their own environment are rather scarce. Read a lot more about the research into why humans sleep less than other primates at Smithsonian.(Image credit: Daniel Ramirez)#sleep #primate #evolution #naturalselection

What's Ahead for Human Evolution?There are some people who believe that humans are no longer evolving, since we've developed civilization and science. When we study the mechanisms of natural selection, we learn how the pressure from predators made us fast runners, and those who had better immune systems were more likely to pass their genes on. But now we have protection in communities and vaccines against disease. While environmental pressures favor certain traits and spur evolution, we haven't moved completely away from the effects of natural selection. The pressures we have today are just different.For one thing, we now live longer. This is partly due to natural selection, and partly due to medical science. The very absence of the pressure to reproduce at young age, lest we die first, allows us to delay having children. This gives those who experience puberty and menopause at a later age a better shot at producing children who survive and carry on those traits. Yet since survival plays a smaller role in when and how much we reproduce, sexual selection plays a larger role. What people find attractive in each other and how we meet someone to reproduce with will affect what kinds of children will result. Real Clear Science looks at how human evolution worked in the past, and speculates on how changing conditions will affect the traits that will proliferate in humans of the future. -via Damn Interesting(Image credit: Tkgd2007)#evolution #humanevolution #naturalselection