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bioRxiv · 10.1101/001289

An Adaptive Threshold in Mammalian Neocortical Evolution

Eric Lewitus·Iva Kelava·Alex T Kalinka·Pavel Tomancak·Wieland B Huttner
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Abstract

Expansion of the neocortex is a hallmark of human evolution. However, it remains an open question what adaptive mechanisms facilitated its expansion. Here we show, using gyrencephaly index (GI) and other physiological and life-history data for 102 mammalian species, that gyrencephaly is an ancestral mammalian trait. We provide evidence that the evolution of a highly folded neocortex, as observed in humans, requires the traversal of a threshold of [~]109 neurons, and that species above and below the threshold exhibit a bimodal distribution of physiological and life-history traits, establishing two phenotypic groups. We identify, using discrete mathematical models, proliferative divisions of pro-genitors in the basal compartment of the developing neocortex as evolutionarily necessary and sufficient for generating a fourteen-fold increase in daily prenatal neuron production and thus traversal of the neuronal threshold. Finally, using RNA-seq data from fetal human neocortical germinal zones, we show a genomic correlate to the neuron threshold in the differential conservation of long intergenic non-coding RNA. (see arXiv:1304.5412)

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Eric Lewitus, Iva Kelava, Alex T Kalinka, Pavel Tomancak, Wieland B Huttner. 2013-12-13. An Adaptive Threshold in Mammalian Neocortical Evolution. https://doi.org/10.1101/001289

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