Partial human skulls about 100,000 years old unearthed in Xuchang, China have been found to present an extraordinary set of features, helping researchers make sense of human evolution in eastern Eurasia.

In a study published in the journal Science, Washington University in St. Louis' Erik Trinkaus and colleagues detailed the mosaic of features they found. The fossils included characteristics from late archaic/early modern humans, Middle Pleistocene Eurasians, and western Eurasian Neanderthals, hinting at possible intermixing.

In terms of features from the late archaic/early modern humans found throughout the Old World, the researchers observed the fossils as having a large size that fitted a large brain, and cranial vaults that were lightly built and had modest brow ridges.

From the Middle Pleistocene eastern Eurasians, the fossils had a low, broad braincase rounding onto the inferior skull, while there were two features from western Eurasian Neanderthals: a detailed rear arrangement and semicircular canal configuration.

Neanderthals died out some 40,000 years ago but their contributions to the gene pool is still highly evident today in how people look and what kind of state their health is in. Thousands of years after the last interbreeding, Neanderthal DNA still influences height and risks for conditions like schizophrenia and lupus by affecting how genes are turned on and off. According to researchers, causal mutation is something people today inherited from Neanderthals.

Eurasian Evolutionary Trends

According to Trinkaus, not a lot is known about the biological nature of modern humans' immediate predecessors within eastern Eurasia based on human fossil records. As such, the discovery of the Xuchang skulls and the resulting assessment of the fossils dramatically increases information about the region's early population.

He also noted that the fossils offer support for a pattern previously identified showing continuity in regional populations within eastern Eurasia, mixed in with long-term trends in connections in populations throughout Eurasia and human biology.

"They reinforce the unity and dynamic nature of human evolution leading up to the modern human emergence," he added.

Supported by the Chinese Academy of Science and the National Science Foundation of China, the current study also featured contributions from Xiao-Mei Nian, Xing Gao, Wu Liu, Li-Ping Zhou, Xiu-Jie Wu, and Zhan-Yang Li.

Factors Affecting Human Evolution

In a study published in the Journal of Applied Phycology, researchers showed that seaweed nutrients may have had a hand in human evolution. Humans diverged from their closest relatives, chimpanzees, about 5 to 7 million years ago and the transition required a host of nutrients that were particularly beneficial to developing bigger brains.

Early humans didn't have a system for tracking food availability so they mostly consumed what was readily available, like seaweeds. They were also able to get their hands on fish, snails, and crustaceans along coastal areas, but seaweeds stood out because they were available all year and could easily be harvested even by children and women.

Crucial nutrients found in seaweeds include taurine, magnesium, zinc, vitamin B12, iodine, and polyunsaturated fatty acids. These nutrients allowed the primitive brain to develop into what it is today and continue to be beneficial to modern brains.

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