Human evolution; Lucy's brain and slow growth infants (Introduction)

by David Turell , Saturday, April 04, 2020, 00:23 (1694 days ago) @ David Turell

A recent study raises the issue of infant growth and dependence:

https://www.sciencedaily.com/releases/2020/04/200403092009.htm

Credit: © CrazyCloud / Adobe Stock

"A new study led by paleoanthropologists Philipp Gunz and Simon Neubauer from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, reveals that Lucy's species Australopithecus afarensis had an ape-like brain. However, the protracted brain growth suggests that -- as is the case in humans -- infants may have had a long dependence on caregivers.

"Contrary to previous claims, the endocranial imprints of Australopithecus afarensis reveal an ape-like brain organization, and no features derived towards humans. However, a comparison of infant and adult endocranial volumes nevertheless indicates more human-like protracted brain growth in Australopithecus afarensis, likely critical for the evolution of a long period of childhood learning in hominins.

"The brains of modern humans are not only much larger than those of our closest living ape relatives, they are also organized differently, and take longer to grow and mature. For example, compared with chimpanzees, modern human infants learn longer at the expense of being entirely dependent on parental care for longer periods of time. Together, these characteristics are important for human cognition and social behavior, but their evolutionary origins remain unclear. Brains do not fossilize, but as the brain grows and expands before and after birth, the tissues surrounding its outer layer leave an imprint in the bony braincase. Based on these endocasts the researchers could measure endocranial volume, and infer key aspects of brain organization from impressions of brain convolutions in the skull.

"A key difference between apes and humans involves the organization of the brain's parietal and occipital lobes...Hypothetically, such brain reorganization in australopiths could have been linked to behaviors that were more complex than those of their great ape relatives (e.g., tool manufacture, mentalizing, and vocal communication). Unfortunately, the lunate sulcus typically does not reproduce well on endocasts, so there is unresolved controversy about its position in australopiths.

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"The pace of dental development of the Dikika infant was broadly comparable to that of chimpanzees and therefore faster than in modern humans. However, given that the brains of Australopithecus afarensis adults were roughly 20 percent larger than those of chimpanzees, the Dikika child's small endocranial volume suggests a prolonged period of brain development relative to chimpanzees. "Even a conservative comparison of the Dikika infant to small-statured and small-brained adults like Lucy, suggests that brain growth in Australopithecus afarensis was protracted as in humans today," explains Simon Neubauer."

Comment: It seems was that Lucy was certainly the start of a of a long road to sapiens.