Predict how will the evolution of humans, it is impossible
We all know how to look Neanderthals: protruding brow ridges, thick nose, elongated skull, a strong bone structure, and probably red hair and freckled skin. You may have looked askance at the red, when you meet in the subway, but maybe not. But you probably would want to look closely at the hunter-gatherers who lived in Europe for 7-8 thousand years ago, a DNA which scientists are currently analyzing.
They had dark skin and, very likely, bright blue eyes. This combination has practically disappeared in ancient Europe - he was replaced by light-skinned and brown-eyed farmers who came from Central Asia for hundreds of years and that, in fact, were similar to the modern population of the south of Europe.
These early farmers who could not live without milk, enjoyed immunity gene for lactose, which was not the old population of hunter-gatherers. They eat a lot less meat, and much more starch than meat-eaters-Europeans, and relied on milk and sunlight as a source of Vitamin D - hence the light skin. As for the dark-skinned and blue-eyed people, they disappeared in Europe because of their genetically gradually replaced intruders.
Here is the story of rapid human evolution. The new principles of life - growing crops and cattle instead of hunting - have led to a rapid expansion of genes that take advantage of these cultural adaptations. Ancient dark skin, probably inherited from our common ancestors from Africa, could be a disadvantage if the majority of calories came from cultivated grain, not the meat of wild animals, rich in vitamin D. blue eyes, however, remained, although the form of a blue eye gene color is recessive and is easily replaced brown eyes. Therefore, after a certain time - it is difficult to say what - the ancient Europeans began to look different. There was also the East Asian genes injected by people with similarities to modern Chukchi and other indigenous Siberian groups closely allied with the Native Americans. Ancient Europe has become a melting furnace, but certain alleles - light skin and brown eyes - came to dominate when the lifestyle of hunter-gatherers changed in connection with the transition to farming and agriculture. We present the evolution described by Charles Darwin in 1859, as a slow dance: nature selects organisms best adapted to reproduction, breeding and survival in a particular ecosystem. As the body adapts to the changing environmental conditions for thousands of years, thrive best adapted to the specific environment of the body, allowing the mind to grow and spread. This process is known as natural selection: organisms best adapted to their environment will give more genes to the next generation, rather than less fit subspecies (of the same species).
The constant change that we see in the fossilized record, takes more time. Just look at the path hoof Hyracotherium, Woodland mammal size of a dog that is gradually lost lateral fingers (four in the front paws and three on the rear), while the central elongated. It took 55 million years to the animal evolved into a giant horse that we are all well known.
Sometimes evolution is moving quickly. As shown by biologists Peter and Rosemary Grant of Princeton University, little beaks can turn into big for just one generation, depending on the climate and the type of food conditions, which can be found on the harsh island. Birds with a small beak may die out, and with a lot - to survive, at least for a while. But these rapid changes are not always forever. Most of these changes is rolled back, again and again. Changes in vegetation can mean that large beaks become uncomfortable. This process of displacement - small changes that occur over short periods of time - called microevolution. Evolutionary biologist David Lahti and Paul Ewald assert that there is nothing exceptional in rapid evolution. Rapid change, temporary or not, simply reflects the intensity of selection, enhanced action "hostile forces of nature," according to Darwin, including predation, heat, cold, parasites. Hard times mean extinction for some species - and rapid evolution to others. But to enable rapid evolution, should be enough genetic variation in the gene pool, that natural selection had plenty to choose from. As in the case of rapid replacement of hunter-gatherers by farmers in ancient Europe. Light-skinned genes have surpassed blacks genes, because it is better suited to life in Europe and a new way of life.
Lahti adds that for those social selection is of paramount importance: the presence of other hostile groups and the human capacity for intra-group cooperation has led to the emergence of social complexity of human and evolution of the human brain. We do not know whether friendly or hostile contacts by European hunters and Middle Eastern farmers. Probably, in ancient Europe it was a collision, as well as the peaceful exchanges. We can not know that we only see the result of an apparent rejection of a single set of features in favor of another, who has settled in a particular area.
Of course, blond hair and fair skin began to characterize Europe in the far north, among the Scandinavian population; there pale skin, probably, was the adaptation to a deficiency of vitamin D. Dark skin is a useful adaptation in hot sunny climates. As the climate changes may occur other local changes in the appearance of the people, we do not know yet. Human evolution and the forces that drive it, they never stopped. Some people will always be preferable from the point of view of natural selection because of their genes, their offspring more likely to survive. This is the essence of natural selection. Adaptation and evolution of man is constantly ongoing. It is impossible to say that we are developing in a particular direction - a big head and frail limbs, as is often said of fiction enthusiasts. But at the local level adaptation and natural selection does not stop its work, preparing us to new threats - new diseases, climate change, new social interactions - unseen and unnoticed.