From fossils to mind

Abstract

Fossil endocasts record features of brains from the past: size, shape, vasculature, and gyrification. These data, alongside experimental and comparative evidence, are needed to resolve questions about brain energetics, cognitive specializations, and developmental plasticity. Through the application of interdisciplinary techniques to the fossil record, paleoneurology has been leading major innovations. Neuroimaging is shedding light on fossil brain organization and behaviors. Inferences about the development and physiology of the brains of extinct species can be experimentally investigated through brain organoids and transgenic models based on ancient DNA. Phylogenetic comparative methods integrate data across species and associate genotypes to phenotypes, and brains to behaviors. Meanwhile, fossil and archeological discoveries continuously contribute new knowledge. Through cooperation, the scientific community can accelerate knowledge acquisition. Sharing digitized museum collections improves the availability of rare fossils and artifacts. Comparative neuroanatomical data are available through online databases, along with tools for their measurement and analysis. In the context of these advances, the paleoneurological record provides ample opportunity for future research. Biomedical and ecological sciences can benefit from paleoneurology's approach to understanding the mind as well as its novel research pipelines that establish connections between neuroanatomy, genes and behavior.

Fig. 1. Time-scaled phylogenetic tree of amniotes.

Included are taxonomic groups covering species discussed in this review and the accompanying “From Fossils to Mind” edited volume. The geological time scale is from Cohen et al.. Phylogeny and time ranges are based on Benton, Kemp, Sues, and Kumar.

Fig. 2. Hominin species time ranges and approximate taxonomic groupings into the three major hominin genera.

In order of first appearance, Australopithecus (yellow), Paranthropus (red) and Homo (blue) species are plotted against a time scale, after Wood et al.. Virtual endocasts are featured to represent each genus.

Fig. 3. Valleculae on the frontal bone of a hadrosaurid dinosaur.

a, b Internal surface of the frontal bone of a hadrosaurid dinosaur (Amurosaurus riabinini, AEHM 1/240) viewed on the left side and right side. Arrows point to some of the valleculae. (Lauters, available at 10.5281/zenodo.7454914).

Fig. 4. Examples of the relationship between hominin fossil hand morphology and early tool use.

a, b A present day human’s hand demonstrating a precision grip when grasping an artifact (a) and a power “squeeze” grip when grasping a hafted artifact (b; both palmar views). Superimposed in turquoise (first metacarpal) and purple (trapezium) are the bones forming the trapeziometacarpal complex at the base of the thumb and responsible for its movements in a present day human (a) and a Neanderthal (Kebara 2; b). (Bardo, available at 10.5281/zenodo.7452329).

Fig. 5. The “From Fossils to Mind” framework.

Endocasts provide information about brain anatomy and vasculature in extinct hominin species, and evidence for their behavior can be gleaned from the archeological record. These data can be interpreted by integrating ancient DNA with new experimental methods at multiple scales (e.g., cell biology, anatomy, genetics, and organoids). To accelerate progress, researchers should collaborate in diverse teams and make their data accessible, findable, and reusable. Created with Biorender.com. Chord diagram done with Flourish (https://app.flourish.studio). The photo of the fossil cast in the center was composited from Australopithecus africanus - Cast of Taung child by Didier Descouens, available under CC BY-SA 4.0 at https://commons.wikimedia.org/wiki/File:Australopithecus_africanus_-_Cast_of_taung_child.jpg.