The intricacies of fetal (right) and placental (left) circulation. The physiology of the circulation in plants, in the lower animals, and in man. 1873.

Branching blood vessels of the placenta.

Die Corrosions-Anatomie und ihre Ergebnisse. Corrosion Anatomy and Its Results. 1873. Photography of photo-based lithography.

The placenta and the hormones it produces may have played a crucial role in the evolution of the human brain, while also leading to the behavioral traits that have made human societies able to thrive and expand, according to a new hypothesis proposed by researchers from the Universities of Cambridge and Oxford. Dr. Alex Tsompanidis, senior researcher at the Autism Research Center at the University of Cambridge, and the lead author of this new study, said, "Small variations in the prenatal levels of steroid hormones, like testosterone and estrogen, can predict the rate of social and cognitive learning in infants and even the likelihood of conditions such as autism. This prompted us to consider their relevance for human evolution."