To get to the bottom of these peculiar human characteristics, Khaitovich and his students are comparing the brain samples of humans, chimpanzees and rhesus monkeys – all at different ages. To be able to gain knowledge on the development of the brain, the team needs pieces of tissue both from newborns and from the very old. And from individuals in a number of different age groups in between.
Finding the right pieces of tissue is a real challenge. Time and again, Khaitovich must persuade other institutes to cooperate, because the samples not only need to be from a human or animal of a certain age, but they also need to come from a specifically defined area of the brain. From the prefrontal cortex, for example – the area behind the brain where inherently human capabilities, such as rational thinking, are located.
The human samples cause Philipp Khaitovich the least problems. He orders them from ‘brain banks’ – facilities where brain tissue from various donors is archived for research purposes. For chimpanzee samples, he is still on good terms with his former professor in Leipzig, where Svante Pääbo several years ago began to archive the brain tissue of apes of various ages; however, it is difficult to get hold of viable brain samples from old macaques. “Rhesus monkeys can live to about 35 years of age, but there are perhaps only a few dozen animals of this age throughout the world.”
The scientists then send the samples from the various elderly humans and monkeys for analysis in partner laboratories to determine gene expressions and other data. For this, they ignore the complicated structure of the brain tissue – the samples contain different types of neurons, glia cells and gray matter. “It is as if two ecosystems, together with all the animals and plants living in them, are being compared with one another.”
Khaitovich is the first to admit that there are weaknesses in this procedure. “This is all still very primitive,” he admits. And at the moment, the technology to investigate the brain comprehensively and look at all the different cell types separately simply does not exist. Nevertheless, Philipp Khaitovich is proud of exploring new avenues: “At least I can say that we are working at the cutting edge of research.”