Humans evolution rapidly evolving

Evolution Human

Evolution Human

 

Humans are evolving more rapidly than previously thought, according to the largest ever genetics study of a single population.

Scientists reached the conclusion after showing that almost every man alive can trace his origins to one common male ancestor who lived about 250,000 years ago. The discovery that so-called “genetic Adam”, lived about 100,000 years more recently than previously understood suggests that humans must have been genetically diverging at a more rapid rate than thought.

Kári Stefánsson, of the company deCODE Genetics and senior author of the study, said: “It means we have evolved faster than we thought.”

The study also shows that the most recent common male ancestor was alive at around the same time as “mitochondrial Eve” – the last woman to whom all females alive today can trace their mitochondrial DNA.

Unlike their biblical counterparts, genetic Adam and Eve were by no means the only humans alive, and although they almost certainly never met, the latest estimate which gives a closer match between their dates makes more sense, according to the researchers.

When the overall population size is stable – as it has been for long periods in the past – men have, on average, just one son, and women, just one daughter. This means that for any given man, there is a high chance that his paternal line will eventually come to an end. This means any male descendants, for instance his daughter’s son, would have Y-chromosomes inherited from other men. If you travelled back far enough in time, the theory goes, there would be only one man whose paternal line extends unbroken to the present day: this man is Y-chromosome Adam.

The researchers dated the existence of this man by comparing the Y-chromsomes of 753 Icelandic men, who were also grouped into 274 paternal lines. The researchers used a “molecular clock”, based on the number of DNA mutations that arise with each generation, to estimate Adam’s age.

The study, published in Nature Genetics, put the new age for genetic Adam at between 174,000 and 321,000 years ago. Genetic Eve is thought to have walked the Earth around 200,000 years ago: well within the new error margin for Adam.

“It gives us enormous confidence to have a timeline that is similar,” said Stefánsson.

Previous dates for ancestral Adam ranged from far more recent, just 50,000 years ago, right back to around 500,000 years ago, with some estimates showing major mismatches with the dating of ancestral Eve. Some researchers had suggested that polygamy could explain the gap, in the cases where Adam was more recent, by reducing the number of men who would pass on their Y-chromosome. Stefánsson describes this argument as a “crock of shit”. “The two sexes are inseparable,” he said. “It doesn’t matter how many women a man has children with – half of them will be boys and half girls.”

Agnar Helgason, also of deCODE, said the latest findings could help refine dates for major events during human evolution, such as when humans first migrated out of Africa and arrived in Europe. “We’re curious about where we came from and when,” he said. “This gives us a bit more solid information about when.”

Previous research also suggested that humans are evolving more quickly now than at any time since the split with the ancestors of modern chimpanzees 6m years ago. The study, by the University of Wisconsin, found that at least 7% of human genes have undergone recent evolution. Some of the changes included the emergence of fair skin and blue eyes in northern Europe, greater resistance to malaria in some African populations and the appearance of a gene that allows lactose to be digested.

 

Source:  theguardian.com

Bees outpace Orchids

 

 

Bees outpace orchids in evolution:

 

 Bees outpace orchids in evolution


Bees outpace orchids in evolution

 

 

Orchid bees aren’t so dependent on orchids after all, according to a new study that challenges the prevailing view of how plants and their insect pollinators evolve together.

A male orchid bee collects fragrance compounds from flowers of a Notylia orchid. Female orchid bees choose mates based upon the mix of these chemical compounds. (R. B. Singer photo)

A long-standing belief among biologists holds that species in highly specialized relationships engage in a continual back-and-forth play of co-evolution.

“What we found was that this reciprocal specialization did not exist for orchid bees and orchids,” said study lead author Santiago Ramirez, post-doctoral researcher in the lab of Neil Tsutsui, associate professor at the University of California, Berkeley’s Department of Environmental Science, Policy, and Management. “The bees evolved much earlier and independently, while the orchids appear to have been catching up.”

The bond between specific bees and the orchid plants they visited has been well-documented by botanists and naturalists, including Charles Darwin. Biologists discovered that male bees needed the specific perfume compounds produced by the flowering plants in order to mate with female bees.

In the study, published in the Sept. 23 issue of the journal Science, the researchers screened more than 7,000 individual male bees and sequenced DNA from 140 orchid pollinaria, which are small packages that contain all the pollen grains produced by a single flower. The researchers were able to infer the evolutionary history of both bees and orchids, and establish which species of bee pollinates what species of orchid. The researchers also quantified and analyzed the perfumes collected by orchid bees and compared them with the compounds produced by orchid flowers.

To their surprise, the scientists found that the bees evolved at least 12 million years earlier than their orchid counterparts. Additionally, they found that the compounds produced by the orchids only accounted for 10 percent of the compounds collected by their pollinators. The remaining 90 percent could be coming from other sources, including tree resins.

Male orchid bees can find the fragrance compounds they need for mating from decaying logs, as shown here, as well as from orchids. (B. Jacobi photo)

“It appears that the male bees evolved a preference to collect these compounds from all kinds of sources, and the orchids converged on that chemical preference millions of years later,” said Ramirez.

In essence, orchids need their bee pollinators more than the bees need them.

The findings have implications in conservation biology, particularly because of the alarming decline over the past 15 years of bee pollinators worldwide.

“Many plant species are extremely dependent on their pollinators,” said Ramirez, who began this work while he was a Ph.D. student in the lab of Naomi Pierce, Harvard University professor of biology. “If you lose one species of bee, you could lose three to four species of orchids. Many of these orchids don’t produce any other type of reward, such as nectar, that would attract other species of bee pollinators.”

“Our study is consistent with the emerging theory that insect sensory biases have played a major role in driving reproductive adaptations in flowering plants,” said Ramirez. “It highlights the ecological and evolutionary inter-dependence of flowering plants and their specialized pollinators, suggesting that new threats to insect pollinators may have profound effects on the ecosystems they inhabit.”