A study puts the burden of humanity’s evolution on our shoulders. Literally on our shoulders. By examining the shoulder blades of two early human Australopithecus species, researchers believe they’ve found further evidence that humans and apes shared an apelike ancestor.

Humans are, of course, most closely related to the great apes of Africa -- chimps and bonobos, specifically. But humans have some features that seem more “primitive,” or more like the monkeys that came earlier in primate lineage, than the analogous features on apes. That’s led some scientists to suggest that our common ancestor was actually more like a monkey while evolving some of the same advanced adaptations as apes.

But according to the study in the Proceedings of the National Academy of Sciences, it’s safe to assume that humans and apes did descend from an apelike ancestor. It’s just that humans got a little turned around along the way.

But by analyzing 3-D scans of shoulder blades from humans, early-human ancestors, apes, and monkeys alike, the researchers concluded that human shoulders do have enough in common with those on apes to have evolved from the ape model.

According to the study authors, our journey from swinging through the trees to making tools and hunting was a long, slow one. But over time, our success with the latter made us give up the former.


Predator-prey mix is consistent

Predators may depend on prey for food, but an increase in the number of prey animals does not bring a proportional increase in the number of predators, a study found.

The analysis, which appears in the journal Science, relies on data from more than 1,000 studies of animals in more than 1,500 locations worldwide. “Looking at this very large scale suggested a level of organization that was previously not recognized,” said Ian A. Hatton, a biologist at McGill University.

Hatton and his colleagues first set out to compare carnivores and herbivores in different ecosystems in Africa, like the Serengeti and the Kalahari. They found a consistent pattern: Numbers of predators do not increase as rapidly as prey.

The pattern could help researchers monitor ecosystems and endangered species. “If we went to India, for example, it could help figure out how many tigers there should be,” Hatton said.


A nursery for newborn stars

A telescope at La Silla Observatory in Chile has captured three clusters of bright newborn stars in the Prawn Nebula, a dense concentration of ionized gas and dust. Just a few million years old, the stars glow in ultraviolet light, illuminating the nebula’s gas clouds as well.

The young stars form from the remnants of old stars that died in supernova explosions. The nebula is about 6,000 light-years from Earth, in the constellation Scorpius.

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