For early man, walking beat talking

A new fossil discovery shows we did not climb out of the trees until much later than once thought.

New study sheds light on how and when vision evolved

Opsins, the light-sensitive proteins key to vision, may have evolved earlier and undergone fewer genetic changes than previously believed, according to a new study from the National University of Ireland Maynooth and the University of Bristol published in Proceedings of the National Academy of Sciences (PNAS) .

The study, which used computer modelling to provide a detailed picture of how and when opsins evolved, sheds light on the origin of sight in animals, including humans. The evolutionary origins of vision remain hotly debated, partly due to inconsistent reports of phylogenetic relationships among the earliest opsin-possessing animals.

Dr Davide Pisani of Bristol’s School of Earth Sciences and colleagues at NUI Maynooth performed a computational analysis to test every hypothesis of opsin evolution proposed to date. The analysis incorporated all available genomic information from all relevant animal lineages, including a newly sequenced group of sponges (Oscarella carmela) and the Cnidarians, a group of animals thought to have possessed the world’s earliest eyes.

Using this information, the researchers developed a timeline with an opsin ancestor common to all groups appearing some 700 million years ago. This opsin was considered ‘blind’ yet underwent key genetic changes over the span of 11 million years that conveyed the ability to detect light.

Dr Pisani said: “The great relevance of our study is that we traced the earliest origin of vision and we found that it originated only once in animals. This is an astonishing discovery because it implies that our study uncovered, in consequence, how and when vision evolved in humans.”

(Image credit: Roland Bircher)

Evolution is actually pretty predictable

“Is evolution predictable? To a surprising extent the answer is ‘yes’,” says Princeton professor Peter Andolfatto.

New research by Andolfatto and colleagues published in the journal Science suggests that knowledge of a species’ genes—and how certain external conditions affect the proteins encoded by those genes—could be used to determine a predictable evolutionary pattern driven by outside factors.

Scientists could then pinpoint how the diversity of adaptations seen in the natural world developed even in distantly related animals.

The researchers carried out a survey of DNA sequences from 29 distantly related insect species, the largest sample of organisms yet examined for a single evolutionary trait. Fourteen of these species have evolved a nearly identical characteristic due to one external influence—they feed on plants that produce cardenolides, a class of steroid-like cardiotoxins that are a natural defense for plants such as milkweed and dogbane.

Though separated by 300 million years of evolution, these diverse insects—which include beetles, butterflies, and aphids—experienced changes to a key protein called sodium-potassium adenosine triphosphatase, or the sodium-potassium pump, which regulates a cell’s crucial sodium-to-potassium ratio.

Did bacteria spark evolution of multicellular life?

Bacteria have a bad rap as agents of disease, but scientists are increasingly discovering their many benefits, such as maintaining a healthy gut.

A new study now suggests that bacteria may also have helped kick off one of the key events in evolution: the leap from one-celled organisms to many-celled organisms, a development that eventually led to all animals, including humans.

Published this month in the inaugural edition of the new online journal eLife, the study by University of California, Berkeley, and Harvard Medical School scientists involves choanoflagellates (aka “choanos”), the closest living relatives of animals. These microscopic, one-celled organisms sport a long tail or flagellum, tentacles for grabbing food and are members of the ocean’s plankton community. As our closest living relative, choanos offer critical insights into the biology of their last common ancestor with animals, a unicellular or colonial organism that lived and died over 650 million years ago.

“Choanoflagellates evolved not long before the origin of animals and may help reveal how animals first evolved,” said senior author Nicole King, UC Berkeley associate professor of molecular and cell biology.

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Yeast experiment offers fresh insights on the nature of natural selection

An experiment involving yeast has revealed a method that allows organizations to avoid the “tragedy of the commons,” the situation in which individuals take advantage of shared resources — such as common grazing land for animals — without paying for their use or maintenance.

By performing the experiment on small organisms, researchers have shown a way to avert a prediction of evolution theory: that natural selection necessarily favors “cheaters” — individual organisms determined to game the system — over “cooperators” who obey the rules.

The experiment, reported in Proceedings of the National Academy of Sciences, reveals a way in which evolutionary adaptation via mutations can benefit cooperators over cheaters.

"It gives a larger role to adaptation," said Adam Waite, a graduate student in molecular and cellular biology at the University of Washington, who performed the research with his supervisor, Wenying Shou, at the Fred Hutchinson Cancer Research Center in Seattle. "While natural selection should help cheaters, it can also help cooperators defeat cheaters."

Death: A special report on the inevitable

The only certain thing in life is that it will one day end. That knowledge is perhaps the defining feature of the human condition. And, as far as we know, we alone are capable of contemplating the prospect of our demise. In these articles we explore the implications: the shifting definition of death, how knowing that we will die gave birth to civilisation, the grim reality of decomposition and whether it makes sense to fear death. But first, when did we become aware of our own mortality?

Computer Simulation Shows Grandmas Made Humans Live Longer

Computer simulations provide new mathematical support for the “grandmother hypothesis” – a famous theory that humans evolved longer adult lifespans than apes because grandmothers helped feed their grandchildren.

“Grandmothering was the initial step toward making us who we are,” says Kristen Hawkes, a distinguished professor of anthropology at the University of Utah and senior author of the new study published Oct. 24 by the British journal Proceedings of the Royal Society B.

The simulations indicate that with only a little bit of grandmothering – and without any assumptions about human brain size – animals with chimpanzee lifespans evolve in less than 60,000 years so they have a human lifespan. Female chimps rarely live past child-bearing years, usually into their 30s and sometimes their 40s. Human females often live decades past their child-bearing years.

The findings showed that from the time adulthood is reached, the simulated creatures lived another 25 years like chimps, yet after 24,000 to 60,000 years of grandmothers caring for grandchildren, the creatures who reached adulthood lived another 49 years – as do human hunter-gatherers.

The grandmother hypothesis says that when grandmothers help feed their grandchildren after weaning, their daughters can produce more children at shorter intervals; the children become younger at weaning but older when they first can feed themselves and when they reach adulthood; and women end up with postmenopausal lifespans just like ours.

By allowing their daughters to have more children, a few ancestral females who lived long enough to become grandmothers passed their longevity genes to more descendants, who had longer adult lifespans as a result.

Evolution of new genes captured

Like job-seekers searching for a new position, living things sometimes have to pick up a new skill if they are going to succeed. Researchers from the University of California, Davis, and Uppsala University, Sweden, have shown for the first time how living organisms do this.

The observation, published Oct. 19 in the journal Science, closes an important gap in the theory of natural selection.

Scientists have long wondered how living things evolve new functions from a limited set of genes. One popular explanation is that genes duplicate by accident; the duplicate undergoes mutations and picks up a new function; and, if that new function is useful, the gene spreads.

"It’s an old idea and it’s clear that this happens," said John Roth, a distinguished professor of microbiology at UC Davis and co-author of the paper.

The problem, Roth said, is that it has been hard to imagine how it occurs. Natural selection is relentlessly efficient in removing mutated genes: Genes that are not positively selected are quickly lost.

How then does a newly duplicated gene stick around long enough to pick up a useful new function that would be a target for positive selection?

Experiments in Roth’s laboratory and elsewhere led to a model for the origin of a novel gene by a process of “innovation, amplification and divergence.” This model has now been tested by Joakim Nasvall, Lei Sun and Dan Andersson at Uppsala.

Complete mitochondrial DNA genome sequences from the first New Zealanders

The dispersal of modern humans across the globe began ∼65,000 y ago when people first left Africa and culminated with the settlement of East Polynesia, which occurred in the last 1,000 y. With the arrival of Polynesian canoes only 750 y ago, Aotearoa/New Zealand became the last major landmass to be permanently settled by humans. We present here complete mitochondrial genome sequences of the likely founding population of Aotearoa/New Zealand recovered from the archaeological site of Wairau Bar. These data represent complete mitochondrial genome sequences from ancient Polynesian voyagers and provide insights into the genetic diversity of human populations in the Pacific at the time of the settlement of East Polynesia.

Raw Food Not Enough to Feed Big Brains

Eating a raw food diet is a recipe for disaster if you’re trying to boost your species’ brainpower. That’s because humans would have to spend more than 9 hours a day eating to get enough energy from unprocessed raw food alone to support our large brains, according to a new study that calculates the energetic costs of growing a bigger brain or body in primates. But our ancestors managed to get enough energy to grow brains that have three times as many neurons as those in apes such as gorillas, chimpanzees, and orangutans. How did they do it? They got cooking, according to a study published online today in the Proceedings of the National Academy of Sciences.

"If you eat only raw food, there are not enough hours in the day to get enough calories to build such a large brain," says Suzana Herculano-Houzel, a neuroscientist at the Federal University of Rio de Janeiro in Brazil who is co-author of the report. "We can afford more neurons, thanks to cooking."

Humans have more brain neurons than any other primate—about 86 billion, on average, compared with about 33 billion neurons in gorillas and 28 billion in chimpanzees. While these extra neurons endow us with many benefits, they come at a price—our brains consume 20% of our body’s energy when resting, compared with 9% in other primates. So a long-standing riddle has been where did our ancestors get that extra energy to expand their minds as they evolved from animals with brains and bodies the size of chimpanzees?

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