Old Understanding

Kevin Lewis

September 16, 2023

Human brains have shrunk: The questions are when and why
Jeremy DeSilva et al.
Frontiers in Ecology and Evolution, June 2023 


Human brain reduction from the Late Pleistocene/Holocene to the modern day is a longstanding anthropological observation documented with numerous lines of independent evidence. In a recent study (DeSilva et al., 2021; Front. Ecol. Evol.), we analyzed a large compilation of fossil and recent human crania and determined that this reduction was surprisingly recent, occurring rapidly within the past 5,000 to 3,000 years of human history. We attributed such a change as a consequence of population growth and cooperative intelligence and drew parallels with similar evolutionary trends in eusocial insects, such as ants. In a reply to our study, Villmoare and Grabowski (2022; Front. Ecol. Evol.) reassessed our findings using portions of our dataset and were unable to detect any reduction in brain volume during this time frame. In this paper, responding to Villmoare and Grabowski’s critique, we reaffirm recent human brain size reduction in the Holocene, and encourage our colleagues to continue to investigate both the timing and causes of brain size reduction in humans in the past 10,000 years.

Anthropomorphism as a contributor to the success of human (Homo sapiens) tool use
Michael Haslam
Journal of Comparative Psychology, August 2023, Pages 200–208 


Humans anthropomorphize: as a result of our evolved ultrasociality, we see the world through person-colored glasses. In this review, I suggest that an interesting proportion of the extraordinary tool-using abilities shown by humans results from our mistakenly anthropomorphizing and forming social relationships with objects and devices. I introduce the term machination to describe this error, sketch an outline of the evidence for it, tie it to intrinsic reward for social interaction, and use it to help explain overimitation -- itself posited as underpinning human technological complexity -- by human children and adults. I also suggest pathways for testing the concept’s presence and limits, with an explicit focus on context-specific individual and temporal variation. I posit cognitive pressure from time constraints or opaque mechanisms as a cause for machination, with rapid, subconscious attribution of goals or desires to tools reducing cognitive overload. Machination holds promise for understanding how we create and use combinatorial technology, for clarifying differences with nonhuman animal tool use, and for examining the human fascination with objects.

Descent, marriage, and residence practices of a 3,800-year-old pastoral community in Central Eurasia
Jens Blöcher et al.
Proceedings of the National Academy of Sciences, 5 September 2023 


Our understanding of prehistoric societal organization at the family level is still limited. Here, we generated genome data from 32 individuals from an approximately 3,800-y-old burial mound attributed to the Bronze Age Srubnaya-Alakul cultural tradition at the site of Nepluyevsky, located in the Southern Ural region of Central Eurasia. We found that life expectancy was generally very low, with adult males living on average 8 y longer than females. A total of 35 first-degree, 40 second-degree, and 48 third-degree biological relationships connected 23 of the studied individuals, allowing us to propose a family tree spanning three generations with six brothers at its center. The oldest of these brothers had eight children with two women and the most children overall, whereas the other relationships were monogamous. Notably, related female children above the age of five were completely absent from the site, and adult females were more genetically diverse than males. These results suggest that biological relationships between male siblings played a structural role in society and that descent group membership was based on patrilineality. Women originated from a larger mating network and moved to join the men, with whom they were buried. Finally, the oldest brother likely held a higher social position, which was expressed in terms of fertility.

The Suburbs of the Early Mesopotamian City of Ur (Tell al-Muqayyar, Iraq)
Emily Hammer & Angelo Di Michele
American Journal of Archaeology, October 2023, Pages 449–479 


Suburbs and other zones of urban sprawl are not recent phenomena; they are as old as cities themselves. However, archaeological investigation of them has been relatively scarce, biasing reconstructions of the scale and diversity of early urban populations, industries, and economies, as well as reconstructions of ancient cities’ size and form. Here, we use aerial and satellite imagery in combination with ground survey to identify and characterize the extramural areas of one of the world’s earliest cities, Ur (Tell al-Muqayyar), in southern Iraq. The results suggest the need for some revisions of earlier impressionistic ideas about the extent, location, and dates of Ur’s suburbs. The distributions of ceramics of periods spanning the fifth to first millennium BCE suggest that Ur may have been founded in the fifth to fourth millennium BCE as a pair of spatially separate settlements that grew at different rates, only one of which developed into the city’s highly mounded core; that more distant suburbs formed by the third millennium BCE; and that intensity of occupation of various extramural zones covering hundreds of hectares shifted throughout the third to first millennium BCE. Overall, the data challenge characterizations of Ur as more compact and spatially continuous than other early Mesopotamian cities.

Infectious diseases may have arrested the southward advance of microblades in Upper Palaeolithic East Asia
Kenichi Aoki et al.
Proceedings of the Royal Society: Biological Sciences, 30 August 2023 


An unsolved archaeological puzzle of the East Asian Upper Palaeolithic is why the southward expansion of an innovative lithic technology represented by microblades stalled at the Qinling–Huaihe Line. It has been suggested that the southward migration of foragers with microblades stopped there, which is consistent with ancient DNA studies showing that populations to the north and south of this line had differentiated genetically by 19 000 years ago. Many infectious pathogens are believed to have been associated with hominins since the Palaeolithic, and zoonotic pathogens in particular are prevalent at lower latitudes, which may have produced a disease barrier. We propose a mathematical model to argue that mortality due to infectious diseases may have arrested the wave-of-advance of the technologically advantaged foragers from the north.


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