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Male Promiscuity Boosts Role of Chance in Sex Chromosome Evolution

Thu, 19 Mar 2015 15:02:31 +0000

Humans, like all mammals and birds, determine sex with chromosomes. Whether a fertilised egg develops into a male or female depends on what chromosomes it carries Scientists have long recognised that genes evolve a little differently on the sex chromosomes, and recent research in GEE suggests this may be due to differing patterns of inheritance […]

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Sloths Move Slow, Evolve Fast

Wed, 11 Mar 2015 18:20:41 +0000

Sloths might be notorious for their leisurely pace of life, but research published last year shows they are no slow coaches when it comes to evolution. Sloths, as we know and love them, are small, slow-moving creatures found in the trees of tropical rainforests. But modern sloths are pretty odd compared to their extinct relatives. […]

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Write About Research – A GEE Research Blog Competition

Tue, 03 Mar 2015 15:28:43 +0000

The GEE Research blog communicates UCL science with a wider, non-specialist audience, by providing short summaries of recent research in the department of UCL Genetics, Evolution and Environment. This provides an opportunity to engage with a broad audience, including other academics, students, members of the public, and even businesses and policy-makers. It is a great […]

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Was Fermentation Key to Yeast Diversification?

Tue, 17 Feb 2015 15:30:43 +0000

From bread to beer, yeast has shaped our diets and our recreation for centuries. Recent research in GEE shows how humans have shaped the evolution of this important microorganism. As well as revealing the evolutionary origins of modern fission yeast, the new study published in Nature Genetics this month shows how techniques developed for detecting […]

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Planning for the Future – Resilience to Extreme Weather

Thu, 15 Jan 2015 15:13:14 +0000

As climate change progresses, extreme weather events are set to increase in frequency, costing billions and causing immeasurable harm to lives and livelihoods. GEE’s Professor Georgina Mace contributed to the recent Royal Society report on “Resilience to Extreme Weather”, which predicts the future impacts of increasing extreme weather events, and evaluates potential strategies for improving […]

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Mother’s care is key to a big brain

7 September 2010

Coverage in the New Scientist

The evolution of big-brained mammals may be due to maternal investment, rather than metabolism, according to a new study by scientists at UCL (University College London) and the University of Cambridge.
Published today in Proceedings of the National Academy of Sciences (PNAS) the study analysed data sets of the brain sizes of 197 marsupial and 457 placental mammals to test the influences of metabolism versus maternal investment on brain size evolution.

MRI brain scan

Contrary to popular hypotheses, researchers found that marsupial mammals, for example kangaroos and possums, had relative brain sizes that are just as big as placental mammals (dogs, horses etc), and even tend to be bigger-brained in some cases.

Big brains in both groups were correlated to length of maternal care, for example a longer period of lactation.  However, basal metabolic rate, or the energy an animal expends at rest, did not correlate with marsupial brain size, whereas they did correlate in placental mammals.  High metabolism was previously thought to be a requirement for big brains as brain tissue is costly to run.

Marsupial brains grow slowly and mainly after birth in the mother’s pouch, whereas placental mammal brains grow rapidly during gestation, where they benefit from the high metabolic rate of the mother.  This study suggests that large brain size can evolve in mammals with low metabolisms as long as they have a period of extended maternal care after birth. 

The researchers also suggest that the evolution of the hugely enlarged brains of some primates can be accounted for by their extended brain growth both during gestation and after birth during a lengthy maternal caring period.

Dr Vera Weisbecker, a joint postdoctoral fellow at the University of Cambridge, Jena University (Germany) and UCL’s Department of Genetics, Evolution & Environment, and lead author of the paper said: “Maternal investment is a much more  universal factor in the evolution of big brains than metabolic rate”.

Dr Anjali Goswami, UCL Department of Genetics, Evolution & Environment and Earth Sciences, and co-author of the paper added, “For a long time, our interest in our own large brains has focused the field on placental characteristics, such as high basal metabolic rate, and made us overlook the role of maternal care after birth on the evolution of big brains. 

“However, if we take primates out of the equation, we discover that marsupials, despite having much lower metabolic rates, have similarly sized brains, or sometimes even bigger brains, than their placental mammal counterparts.  So clearly, evolving big brains isn’t just about having a high metabolism.  Instead, it seems that maternal care is the most consistent factor driving the development of big brains across all mammals.”

Brain development in the two groups is a case of ‘the hare and the tortoise’.  Placental mammals are the ‘hares’ – their brains develop very fast during gestation, with relatively little growth after birth.  Marsupials are the ‘tortoises’ – they are born with very little of their brain developed but then grow slowly and steadily for an extended period after birth whilst they are  being cared for by their mothers.

“It appears that primate brains benefit from the best of both methods of increasing brain size – their brains grow rapidly during gestation in line with their fellow placental mammals, but also develop significantly after birth during a maternal care period which is only comparable to marsupials in terms of length,” added Dr Goswami.

The research was funded by a Volkswagen Foundation Evolution Initiative Postdoctoral Fellowship Grant to V Weisbecker.

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