2009 Science News of the Year: Humans

An artist's illustration shows how a female Ardipithecus may have looked. An analysis of Ardi's bones, uncovered from 1992 through 1997, was released this year. Credit: J.H. Matternes
An artist’s illustration shows how a female Ardipithecus may have looked. An analysis of Ardi’s bones, uncovered from 1992 through 1997, was released this year. Credit: J.H. Matternes
Ardi puts new spin on hominid evolution A 4.4-million-year-old partial female skeleton discovered in Africa, along with fossils from at least 36 of her comrades, provide the first comprehensive look at any ancient hominid species older than Lucy ( SN: 10/24/09, p. 9 ). The skeleton, dubbed Ardi, looks unlike any living primate, suggesting that today’s chimps provide poor models of the last common ancestor of humans and African apes, researchers assert. “ Ardipithecus is so rife with anatomical surprises that no one could have imagined it without direct fossil evidence,” says Tim White of the University of California, Berkeley.

Ardi’s species, Ardipithecus ramidus, lived in a forested region and possessed an unexpected mix of skeletal traits suitable for two-legged walking at a slow pace, for methodical tree climbing and for movement through the trees on all fours, the researchers say. Small faces and canine teeth indicate that males rarely fought over access to mates, unlike male chimps. Instead, Ardipithecus males gathered food and brought it to specific females. This mating style spurred the evolution of an upright stance and the sexual physiology of women today, according to one of the Ardi investigators.

Mental disorders double up
Depression, anxiety disorders, alcohol dependence and marijuana dependence affect roughly twice as many people as had previously been estimated, a new study finds (SN: 10/10/09, p. 5).

New world in tandem
The first Americans may have traveled across a land bridge and south from Alaska in two separate groups at about the same time (SN: 1/31/09, p. 5).

Universal, musical feelings
African farmers with no exposure to Western media provide the first solid evidence of a universal human ability to distinguish basic emotions in music (SN: 4/11/09, p. 14).

Ancient sculpture
An archaeologist discovers an ivory figurine of a woman with exaggerated features that may date to more than 35,000 years ago, making it the oldest known example of art depicting the human body (SN: 6/20/09, p. 11).

Smart hobbits
A controversial, humanlike species that lived in Indonesia 18,000 years ago evolved a chimp-sized brain organized in ways that fostered complex thought necessary for toolmaking, a new study concludes (SN: 4/25/09, p. 9).

Fire engineers
People in southern Africa heated stones in preparation for toolmaking 72,000 years ago (SN: 9/12/09, p. 15).

Horse tamers
Scientists find the earliest evidence of horse domestication, a key event in cultural evolution, at 5,000-year-old sites in central Asia (SN: 3/28/09, p. 15).

Stepping back
Excavations in Kenya yield ancient footprints indicating that Homo erectus had a nearly modern human foot and walking style about 1.5 million years ago (SN: 3/28/09, p. 14).

Symbolic scratches
Engraved patterns on pieces of pigment (right) found in a Stone Age cave indicate that a tradition of creating symbolic designs existed in southern Africa from 75,000 to 100,000 years ago (SN Online: 6/12/09).

Sex-role surprise
Men and women play the mating game with flexible sets of rules, finds an analysis of data from 18 societies, including the Aka in the Central African Republic (shown above). The findings challenge the popular idea that males evolved to be promiscuous and females to be selective (SN: 5/23/09, p. 5).

Fathers and intelligence
Children with older fathers score lower on cognitive tests than those with younger fathers, a study finds (SN Online: 3/9/09).

Twine time
Excavations at a cave in western Asia suggest that, as early as 32,000 years ago, hunter-gatherers made wild flax fibers into cords, probably for sewing clothes, weaving baskets and attaching stone tools to handles (SN Online: 9/10/09).

Contested cannibalism
A research team argues that hundreds of people were butchered and eaten at a 7,000-year-old German site (SN: 1/2/10, p. 10).

Lost in circle-ation
Deprived of the sun or other external navigational cues, people’s feet lead them in circles (SN: 9/12/09, p. 14).

All about the context
A visual illusion stumps adults but not kids, suggesting that sensitivity to visual context develops slowly (SN Online: 11/20/09).

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