Human Brain Evolution: 2 Studies Examined

[pinball1970]

Two studies on human brain evolution/development.

FIRST

A new study is the first to identify how human brains grow much larger, with three times as many neurons, compared with chimpanzee and gorilla brains. The study identified a key molecular switch that can make ape brain organoids grow more like human organoids, and vice versa.

Article

https://www.sciencedaily.com/releases/2021/03/210324113502.htm

Paper

https://www.cell.com/cell/fulltext/...m/retrieve/pii/S0092867421002397?showall=true

SECOND

The brains of modern humans differ from those of great apes in size, shape, and cortical organization, notably in frontal lobe areas involved in complex cognitive tasks, such as social cognition, tool use, and language. When these differences arose during human evolution is a question of ongoing debate. Here, we show that the brains of early Homo from Africa and Western Asia (Dmanisi) retained a primitive, great ape–like organization of the frontal lobe. By contrast, African Homo younger than 1.5 million years ago, as well as all Southeast Asian Homo erectus, exhibited a more derived, humanlike brain organization. Frontal lobe reorganization, once considered a hallmark of earliest Homo in Africa, thus evolved comparatively late, and long after Homo first dispersed from Africa

Paper

https://science.sciencemag.org/content/372/6538/165

 

[Laroxe]

I can see two particular problems with using this impressive technology in this way. The first is in the assumption that the structure of the primate brain tells us something about particular cognitive abilities, of course there is a correlation but the trend to try and fine tune these associations is problematic. Simply because the human brain is structurally different doesn't tell us much about the cognitive ability of early humans. In fact all the skills mentioned are present in various degrees in other animals, some with no frontal cortex as such, some birds for example. Of course, we have no comparative data on other hominins and its difficult to know why the authors describe the brains of non-modern humans as primitive, some primates are quite as current as we are.

Perhaps more importantly is the issue of using organoids to make predictions of the future organisation of the brain. Organoids are created in vitro and at best represent the very early stages of brain development but lacking many of the growth factors and structural ques. In fact they are often useful in examining the function of specific neurochemicals or very particular cells/tissues, they are in no way useful models for the later brain development, or development in vivo. They are most useful to study neurones at the cellular level. and most organoids are created with a particular area of study in mind.

https://www.nature.com/articles/s41592-020-0964-z