Эрдэмтэд эртний хүмүүсийн мөчдийн ясанд хийсэн шинжилгээгээр тэдний амьдралын хэв маяг болон хөдөлгөөний хувьслын үе шатыг тодорхойлжээ.
АНУ-ын Өмнөд Калифорнийн их сургуулийн Кек анагаах ухааны сургуулийн судлаачид 1.5-аас 3.7 сая жилийн настай, Австралопитек болон эртний Хомо төрлийн долоон хүний үлдэгдэлд компьютер томографын шинжилгээ хийжээ. Ясны бүтэц, түүний гулзайлт болон мушгиралтад тэсвэртэй байдлыг хэмжсэнээр эдгээр өвөг дээдэс хэрхэн хөдөлдөг байсныг тогтоосон байна. Шинжилгээний үр дүнг Science Advances сэтгүүлд нийтэлжээ.
Судалгаагаар Австралопитекууд модны амьдрал болон газар дээрх алхалтыг хослуулсан, өнөөгийн амьтдын аль алинд нь үл ажиглагдах өвөрмөц хөдөлгөөний хэв маягтай байсныг илрүүлэв. Тэдний гарын яс нь сармагчингийнхтай төстэй хүчтэй байсан бол хөлийн яс нь орчин үеийн хүмүүсийнхтэй адил алхалтад зохицсон бүтэцтэй байжээ. Энэ нь тэднийг модны амьдралаас бүрэн хөндийрөөгүй байсныг нотолж байна.
Харин 1.8-аас 2.3 сая жилийн өмнө амьдарч байсан эртний Хомо төрлийн хүмүүсийн ясны бүтэц нь орчин үеийн хүмүүстэй илүү төстэй болсон байв. Тэдний гуяны яс гарын яснаас харьцангуй хүчтэй болсон нь газар дээр илүү их алхдаг болсныг илтгэж байна. Судлаачид үүнийг Австралопитекээс Хомо руу шилжих үеийн зан үйлийн үндсэн өөрчлөлт гэж үзэж байна.
Энэхүү хөдөлгөөний өөрчлөлт нь тархины хэмжээ огцом томорсон үетэй давхцаж байгаа нь анхаарал татаж байна. Судлаачид газар дээр илүү хол алхах болсон нь бие махбод болон тархинд шинэ шаардлага тавьж, улмаар хувьслын энэхүү өөрчлөлтөд нөлөөлсөн байж болзошгүй хэмээн таамаглаж байна. Гэсэн хэдий ч энэ нь одоогоор батлагдаагүй, судлаачдын дэвшүүлж буй таамаглал юм.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
A new analysis of fossilized limb bones suggests that Australopithecus, an early human ancestor, combined substantial time in trees with a way of using its legs that resembled our own. The study, led by the Keck School of Medicine of USC, also points to a major change in movement around the transition between Australopithecus and early Homo.
Walking on two legs, known as bipedalism, is a defining feature of humans compared with other apes. Australopithecus lived roughly 2 million to 4 million years ago, and for these ancestors, walking upright did not necessarily mean leaving the trees behind.
The research tackles a question about when our ancestors shifted from moving both through trees and across the ground to living almost entirely on the ground. An international team investigated, using fossils from seven individuals belonging to Australopithecus and its descendants, early Homo. The fossils ranged from about 1.5 million to 3.7 million years old, and the results appeared in Science Advances.
How Bones Reveal the Lives People Lived?
Bones adapt to the forces placed on them, which is why they can say something about an individual’s life. Animals that regularly move through trees tend to have relatively strong arm bones, while humans who walk upright on the ground tend to have stronger thigh bones. Comparing those strengths offers evidence of how an individual used its limbs, and it complements studies of skeletal features that evolved over many generations.
To get at that evidence, the researchers turned to computed tomography (CT) scans, which use X-rays to produce detailed images of bones and their internal structure. The team measured the thickness and structure of the bone shafts and estimated their resistance to bending and twisting. They then compared the upper arm, thigh, and shin bones within each individual.
Two Patterns, One Clear Divide
The early Homo individuals, who lived about 1.8 million to 2.3 million years ago, showed a pattern resembling modern humans. Their thigh bones were relatively strong compared with their arm bones, suggesting a greater reliance on walking on the ground. The results support the idea that a substantial behavioral shift had occurred by roughly 2 million years ago.
Kristian J. Carlson, the study’s lead author and a professor of clinical medical education at the Keck School of Medicine, framed the finding in a particular way.
“We’re proposing that relative limb strength is a ‘threshold trait’—a difference that marks an important and fundamental shift in behavior between Australopithecus and Homo,” he said.
Australopithecus told a different story. Their arms were strong relative to their thighs, much like those of modern apes. Within the legs, though, the relationship between thigh and shin strength followed a more human-like pattern. The comparisons suggest the upper limbs stayed important for moving through trees while the lower limbs supported upright walking.
“Australopithecus combined an ape-like upper limb strength with a human-like pattern in the legs, suggesting they had a unique movement strategy that has no modern comparison,”explained Carlson.
Did They Live in Trees or on the Ground?
That combination bears directly on a longstanding disagreement about how much time Australopithecus spent in each environment. Some researchers have argued that these ancestors mostly walked upright on the ground. Carlson says the new evidence instead suggests that movement in trees remained a substantial part of their lives.
The shift in limb use roughly coincides with the beginning of a dramatic increase in brain size. Scientists have proposed explanations for that growth involving language, tool use, and changes in how human ancestors found food. The study team suggest that walking greater distances on the ground may help connect the changes in limb strength and brain size. The idea is openly speculative. In Carlson‘s words:
“We speculate that the shift toward more walking may have placed new demands on the body and brain, which could help explain why these changes happened around the same time.”
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