Adapiforms, which are not directly related to humans, evolved after the earliest primate ancestors, called plesiadapiforms, which lived about 65 million years ago. Harrington and colleagues created virtual endocasts for three different species of adapiforms: Notharctus tenebrosus and Smilodectes gracilis from the middle Eocene Bridger formation of Wyoming and a late Eocene European specimen named Adapis parisiensis.
Adapiforms' skulls differ from the earlier plesiadapiforms in a few ways including having more forward-facing eyes. Thanks to the new virtual endocasts, scientists were able to take a closer look at anatomical features which revealed that, while adapiforms placed relatively less emphasis on smell more similar to modern primate brains, the relative brain size was not so different from that of plesiadapiforms, said study co-author Jonathan Bloch, curator of vertebrate paleontology at the Florida Museum.
Modern primates are specialized in the visual sense. One of the main differences between the early plesiadapiforms and adapiforms is the region of the brain responsible for the sense of smell, the olfactory bulb, is smaller, while there appears to be an expansion in the area of the brains responsible for vision, Harrington said.
Scientists say that by indirectly manipulating bee behaviour to improve pollination of infected plants by changing their scent, the virus is effectively paying its host back. This may also benefit the virus: helping to spread the pollen of plants susceptible to infection and, in doing so, inhibiting the chance of virus-resistant plant strains emerging.
The authors of the new study, published today in the journal PLOS Pathogens, say that understanding the smells that attract bees, and reproducing these artificially by using similar chemical blends, may enable growers to protect or even enhance yields of bee-pollinated crops.
Through mass spectrometry, researchers could see the change in emissions induced by the virus. They also found that bumblebees could smell the changes. Released one by one in a small 'flight arena' in the Botanic Gardens, and timed with a stopwatch by researchers, the bees consistently headed to the infected plants first, and spent longer at those plants. "Bees are far more sensitive to the blends of volatiles emitted by plants and can detect very subtle differences in the mix of chemicals. In fact, they can even be trained to detect traces of chemicals emitted by synthetic substances, including explosives and drugs," said Carr.
Not only is CMV one of the most damaging viruses for horticultural crops, but it also persists in wild plant populations, and Carr says the new findings may explain why: "We were surprised that bees liked the smell of the plants infected with the virus - it made no sense. You'd think the pollinators would prefer a healthy plant. However, modelling suggested that if pollinators were biased towards diseased plants in the wild, this could short-circuit natural selection for disease resistance," he said.
Mathematical modelling by plant disease epidemiologist Dr Nik Cunniffe, also in the Department of Plant Sciences at Cambridge, explored how the experimental findings apply outside the glasshouse. The model showed how pollinator bias for infected plants can cause genes for disease-susceptibility to persist in plant populations over extremely large numbers of generations.
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In her popular science book The Human Advantage: A New Understanding of How Our Brain Became Remarkable (MIT Press: March 2016), Herculano-Houzel explains how human brains grew so large, even larger than the brains of gorillas and orangutans, whose bodies are larger than ours. Her answer is surprisingly simple. It is the invention of cooking.
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What is nastic movement due to growth?This ability is believed to have evolved only in humans. For example, given prior experience with the ingredients, but in the absence of direct experience with the mixture, only humans are thought to be able to predict that lemonade tastes better with sugar than without it. In contrast, all other animals are thought to be stuck in their previous experiences. At best, they should be able to predict that the juice they tasted before will taste the same again. But they would be unable to realize that a novel mixture of known juices will have new gustatory qualities, which depend on those of the ingredients. Faced with such new situations, animals are expected to be clueless and act by trial-and-error.