Encephalization and longevity evolved in a correlated fashion in Euarchontoglires but not in other mammals

Abstract

Across mammals, encephalization and longevity show a strong correlation. It is not clear, however, whether these traits evolved in a correlated fashion within mammalian orders, or when they do, whether one trait drives changes in the other. Here, we compared independent and correlated evolutionary models to identify instances of correlated evolution within six mammalian orders. In cases of correlated evolution, we subsequently examined transition patterns between small/large relative brain size and short/long lifespan. In four mammalian orders, these traits evolved independently. This may reflect constraints related to energy allocation, predation avoidance tactics, and reproductive strategies. Within both primates and rodents, and their parent clade Euarchontoglires, we found evidence for correlated evolution. In primates, transition patterns suggest relatively larger brains likely facilitated the evolution of long lifespans. Because larger brains prolong development and reduce fertility rates, they may be compensated for with longer lifespans. Furthermore, encephalization may enable cognitively-complex strategies that reduce extrinsic mortality. Rodents show an inverse pattern of correlated evolution, whereby long lifespans appear to have facilitated the evolution of relatively larger brains. This may be because longer lived organisms have more to gain from investment in encephalization. Together, our results provide evidence for the correlated evolution of encephalization and longevity, but only in some mammalian orders.

Need for speed: Short lifespan selects for increased learning ability

“…We want to emphasize that this finding does not necessarily contradict the logic that a long lifespan can help to recoup investment as postulated e.g. by the “delayed benefit hypothesis” 7–9 . However, we suggest that the effect of longevity on cognitive abilities and enlarged brains can work in opposing directions.…”

“…Yet, whether parental care is a consequence or driver for the evolution of increased cognitive abilities is a matter of debate see e.g. 9 . In general, we may expect short-lived animals to solve some cognitive tasks faster than slightly longer-lived species from a similar niche.…”

“…Neuronal systems are metabolically extremely expensive 5,6 therefore raising the question what ecological conditions make this investment worthwhile. This gave rise to the idea that an investment in cognitive abilities is particularly beneficial for long-lived species, as a long lifespan offers more opportunities to recoup the initial investment (sometimes referred to as “delayed benefits hypothesis” 7–9 ). Indeed, many studies superficially support this explanation, showing a positive correlation of enlarged brains, cognitive abilities and longevity e.g.…”

“…Nonetheless, the “delayed benefits hypothesis” is considered to describe a major factor in the evolution of animal intelligence, that may explain the correlation between enlarged brains and longevity e.g. 7,9 .…”

Pollen feeding inHeliconiusbutterflies: the singular evolution of an adaptive suite

“…Finally, a decrease in adult mortality owing to predation, together with a delay of reproductive senescence, probably strengthened selection for extended lifespans (figure 3, yellow). An increase in longevity would also favour investment in learning, long-term memory and their neural correlates ( figure 3, pink), which is less rewarding for shorter-lived species [94,95]. However, this interaction may itself require concomitant investment trade-offs or physiological adaptations, as the costs of learning can cause reductions in longevity [103], and fecundity [104].…”