Education-Science

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Early humans domesticated themselves, new genetic evidence suggests

ScienceMag 12/2019

Domestication encompasses a whole suite of genetic changes that arise as a species is bred to be friendlier and less aggressive. In dogs and domesticated foxes, for example, many changes are physical: smaller teeth and skulls, floppy ears, and shorter, curlier tails. Those physical changes have all been linked to the fact that domesticated animals have fewer of a certain type of stem cell, called neural crest stem cells.

Modern humans are also less aggressive and more cooperative than many of our ancestors. And we, too, exhibit a significant physical change: Though our brains are big, our skulls are smaller, and our brow ridges are less pronounced. So, did we domesticate ourselves?

Giuseppe Testa, a molecular biologist at University of Milan in Italy, and colleagues knew that one gene, BAZ1B, plays an important role in orchestrating the movements of neural crest cells. Most people have two copies of this gene. Curiously, one copy of BAZ1B, along with a handful of others, is missing in people with Williams-Beuren syndrome, a disorder linked to cognitive impairments, smaller skulls, elfinlike facial features, and extreme friendliness.

Newly Discovered Fossil Bird Fills in Gap Between Dinosaurs and Modern Fliers

Smithsonian Mag 11/14/19

The 120 million-year-old fossil was discovered in the summer of 2013 while searching for fossils at Japan’s Kitadani Dinosaur Quarry. “One of my colleagues at Fukui Prefectural Dinosaur Museum spotted tiny bones in a block of siltstone,” Imai says. At the time, it wasn’t clear what creature the bones belonged to, but once the encasing rock was chipped away, the structure of the fossil became clear. The skeleton was an early bird, and an unusual one at that.

Small bodies and hollow bones have made birds relatively rare finds in the fossil record. Only a few unique fossil deposits, like China’s 125 million-year-old Jehol Biota or the United States’ 50 million-year-old Green River Formation, allow paleontologists to get a good look at ancient avians. To find a well-preserved fossil bird outside such places of exceptional preservation represents a noteworthy paleontological discovery, and Fukuipteryx in Japan adds another significant spot on the map for fossil birds.

'Dragon teeth’ reveal ancient ape’s place in primate family tree

Science Mag 11/13/2019

In 1935, anthropologist Gustav von Koenigswald came across several strange teeth in drug stores in Hong Kong and southern China. The specimens, sold as “dragon teeth,” to be ground up for use in Chinese medicine, were special: They were apelike, but huge—much bigger than the molars of any other fossil or living primates. Their size (and that of four fossilized jaw bones) suggested that Gigantopithecus blacki was the largest primate ever discovered, towering nearly 3 meters in height(9 feet). But without any skulls or skeletons, researchers didn’t know whether the animal, which lived from roughly 2 million to 200,000 years ago, was a relative of today’s orangutans, today’s African apes, or something else entirely.

Frido Welker, an evolutionary geneticist at the University of Copenhagen, and his colleagues set out to examine G. blacki teeth for intact pieces of proteins called peptides, which may be preserved for up to a few million years—far longer than more fragile DNA. Welker and his colleagues dissolved tiny amounts of enamel from a G. blacki molar and used mass spectrometry to identify more than 500 peptides that matched six proteins. By comparing the amino acids to those in the same six proteins in living apes, including orangutans, gorillas, and other apes and monkeys, they calculated that the giant ape was most closely related to orangutans. The two lineages probably split off between 10 million and 12 million years ago, they report today in Nature.

Is Evolution Predictable? Important Implications for the Way We Understand Life on Earth

SciTech Daily 11/15/2109

“Our team is the first to report that although evolution of similar color patterns in Heliconius may be driven by similar forces–like predators avoiding a particular kind of butterfly–the pathway to that outcome is not predictable,” said Carolina Concha, lead author of the paper and a post-doctoral fellow at STRI. “This really surprised us because it reveals the importance of history and chance in shaping the genetic pathways leading to butterfly wing-pattern mimicry.”

Heliconius‘ bright wing colors signal to bird predators that the butterflies are toxic. Flashy male wing patterns signal to females that they are choosing the right species to mate with. Somehow these two forces, predation and mating, lead to similar wing patterns in groups of butterflies isolated in the mountain valleys and foothills of the Andes. By knocking out a single gene called WntA in 12 different species and their variants, the molecular biologists on the team could tell whether the butterflies in a pair with the same wing patterns were using the same genetic pathways to color and pattern their wings. They were not.