By the time a baby is born, its brain has lost large numbers of neurons with genetic abnormalities. Credit: Getty

Around the time of birth, the developing human brain mysteriously tidies up by purging itself of a vast number of mutation-riddled neurons, according to a painstaking analysis of more than 2,300 nerve cells.

We are all mosaics: vast genetic diversity found between cells in a single person

The analysis, published in Nature 1 on 28 October, found that more than one-quarter of the sampled neurons from the brains of human fetuses had either gained or lost several segments of their chromosomes. By contrast, only about 6% of neurons from the brains of babies after birth had such abnormalities.…