2011 Science News of the Year: Humans
While the Han Chinese (left) don’t show genetic contributions from Denisovans, Australian Aborigines (right) do.
BLACKRED/ISTOCKPHOTO; GARY RADLER/ISTOCKPHOTO
Asia takes a bow
Often overlooked as a geographic player in human evolution, Asia has stepped into the scientific spotlight. New comparisons of ancient and modern DNA indicate that Stone Age humans migrated to Asia in two stages.
At least 44,000 years ago, initial arrivals in Southeast Asia interbred with a humanlike population known as Denisovans that apparently had spread southward from Siberia. Denisovans contributed a portion of genes to living New Guineans (SN: 1/15/11, p. 10), Australian Aborigines and groups on nearby islands (SN: 11/5/11, p. 13). A second human influx gave rise to today’s East Asians, with no Denisovan dalliances, starting between 38,000 and 25,000 years ago, geneticist Morten Rasmussen of the Natural History Museum of Denmark in Copenhagen and his colleagues find. The work builds on previous genetic evidence that Homo sapiens interbred with Neandertals in West Asia before heading east.
Another study raises the possibility that early members of the genus Homo evolved in Asia and then trekked to Africa, not vice versa as many scientists have assumed (SN: 7/2/11/, p. 8). Homo erectus inhabited a West Asian site called Dmanisi from 1.85 million to 1.77 million years ago, at the same time or slightly before the earliest evidence for the species in Africa, researchers report. —Bruce Bower
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Ape to human Skeletal traits in the proposed hominid species Australopithecus sediba suggest that the species served as an evolutionary bridge from apelike ancestors to the Homo genus (SN: 10/22/11, p. 14).
Fast track Modern humans reached Arabia’s eastern edge as early as 125,000 years ago, 65,000 years earlier than generally accepted migrations out of Africa, scientists report (SN: 2/26/11, p. 5).
Hormone’s dark side The brain-altering substance oxytocin amplifies whatever social proclivities a person already possesses, encouraging a trusting person to be more trusting but a suspicious person to be more uncooperative and hostile (SN: 2/26/11, p. 15).
Clovis question Stone tools and flaky rock bits in Texas date to between 13,200 and 15,500 years ago, adding to evidence that the Clovis people were not the first in the Americas (SN: 4/23/11, p. 12).
Easy geometry Mundurucú villagers of the Amazon grasp abstract geometric principles despite having no formal math education, suggesting geometry is innate or learned through general experience (SN: 6/18/11, p. 16).
Built to walk A 3.2-million-year-old fossil from East Africa suggests Australopithecus afarensis, best known from the partial skeleton “Lucy,” had stiff foot arches like those of people today, a sign of a two-legged stride (SN: 3/12/11, p. 8).
Oldest axes An East African site yields the oldest known stone hand axes, dating to 1.76 million years ago (SN: 10/8/11, p. 12).
Filled belly A 5,300-year-old mummy known as “the Iceman” dined on wild goat before his death in the Italian Alps (SN: 9/24/11, p. 8).
Write stuff Writing down test-related worries before an exam appears to dislodge concerns and lead to higher achievement among high school and college students (SN: 2/12/11, p. 9).
Paint shop In a cave along South Africa’s coast, Stone Age humans made a red-hued paint that they stored in abalone shells and possibly used to decorate themselves or their belongings (SN: 11/19/11, p. 16).
No poker face People can tell whether a chimp acts dominantly and is physically active just by looking at a picture of its expressionless mug. The ability to discern personality traits via facial structure may have evolved more than 7 million years ago, researchers argue (SN: 2/12/11, p. 8).
Share or stash If they’ve worked together to get it, young kids share stuff equally. Adult chimps don’t mete out fair shares, suggesting sharing evolved in ancient human foraging groups ( SN: 8/27/11, p. 10).