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The Best of Both Worlds:Planning for Ecosystem Win-Wins

Sun, 16 Nov 2014 12:25:44 +0000

The normal and healthy function of ecosystems is not only of importance in conserving biodiversity, it is of utmost importance for human wellbeing as well. Ecosystems provide us with a wealth of valuable ecosystem services from food to clean water and fuel, without which our societies would crumble. However it is rare that only a […]

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Planning for Ecosystem Win-Wins
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Life Aquatic: Diversity and Endemism in Freshwater Ecosystems

Thu, 06 Nov 2014 11:22:07 +0000

Freshwater ecosystems are ecologically important, providing a home to hundreds of thousands of species and offering us vital ecosystem servies. However, many freshwater species are currently threatened by habitat loss, pollution, disease and invasive species. Recent research from GEE indicates that freshwater species are at greater risk of extinction than terrestrial species. Using data on […]

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Diversity and Endemism in Freshwater Ecosystems
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Handicaps, Honesty and VisibilityWhy Are Ornaments Always Exaggerated?

Thu, 23 Oct 2014 13:30:30 +0000

Sexual selection is a form of natural selection that favours traits that increase mating success, often at the expense of survival. It is responsible for a huge variety of characteristics and behaviours we observe in nature, and most conspicuously, sexual selection explains the elaborate ornaments such as the antlers of red deer and the tail […]

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Why Are Ornaments Always Exaggerated?
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PREDICTS Project: Land-Use Change Doesn’t Impact All Biodiversity Equally

Mon, 13 Oct 2014 09:17:53 +0000

Humans are destroying, degrading and depleting our tropical forests at an alarming rate. Every minute, an area of Amazonian rainforest equivalent to 50 football pitches is cleared of its trees, vegetation and wildlife. Across the globe, tropical and sub-tropical forests are being cut down to make way for expanding towns and cities, for agricultural land […]

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Calculated Risks: Foraging and Predator Avoidance in Rodents

Fri, 03 Oct 2014 10:07:08 +0000

Finding food is one of the most important tasks for any animal – most animal activity is focused on this job. But finding food usually involves some risks – leaving the safety of your burrow or nest to go out into a dangerous world full of predators, disease and natural hazards. Animals should therefore be […]

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Foraging and Predator Avoidance in Rodents
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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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