Scientists find microplastics in blood for first time
Scientists have discovered microplastics in human blood for the first time, warning that the ubiquitous particles could also be making their way into organs.
Scientists have discovered microplastics in human blood for the first time, warning that the ubiquitous particles could also be making their way into organs.
Environment
Mar 25, 2022
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A University of Adelaide-led project has overturned the theory that the evolution of human intelligence was simply related to the size of the brain—but rather linked more closely to the supply of blood to the brain.
Evolution
Aug 30, 2016
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Farm animals look different from their wild counterparts in many ways, and one difference is consistent: their brains are smaller than those of their ancestors. From sheep to pigs to cows, domesticated animals have smaller ...
Plants & Animals
Jul 5, 2023
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Parrots are famous for their remarkable cognitive abilities and exceptionally long lifespans. Now, a study led by Max Planck researchers has shown that one of these traits has likely been caused by the other. By examining ...
Plants & Animals
Mar 29, 2022
1
384
A study led by researchers at Lund University in Sweden shows that ravens are as clever as chimpanzees, despite having much smaller brains, indicating that rather than the size of the brain, the neuronal density and the structure ...
Plants & Animals
Apr 26, 2016
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(PhysOrg.com) -- At Britain's Royal Society, Dr. Marta Lahr from Cambridge University's Leverhulme Centre for Human Evolutionary Studies presented her findings that the height and brain size of modern-day humans is shrinking.
Human brains have shrunk over the past 30,000 years, puzzling scientists who argue it is not a sign we are growing dumber but that evolution is making the key motor leaner and more efficient.
Evolution
Feb 6, 2011
56
1
Sixty-six million years ago, an asteroid hit the Earth with the force of 10 billion atomic bombs and changed the course of evolution. The skies darkened and plants stopped photosynthesising. The plants died, then the animals ...
Evolution
Nov 26, 2022
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389
The relatively large size of the mammalian brain evolved due to a capacity for endurance exercise, researchers conclude in a recent study.
Plants & Animals
Aug 4, 2011
18
0
A new study in Frontiers in Ecology and Evolution suggests that birds have two alternative strategies for coping with the difficulties of humanity's increasingly chaotic cities—either by having large brains or through more ...
Evolution
Mar 25, 2020
2
702
There has been quite a bit of study of the relationships between brain size, body size, and other variables across a wide range of species, largely because the easiest way to study any object is to measure its size. Even for extinct species brain size can be estimated by measuring the cavity inside the skull. The story that emerges, however, is complex.
As might be expected, brain size tends to increase with body size (measured by weight, which is roughly equivalent to volume). The relationship is not a strict proportionality, though: averaging across all orders of mammals, it follows a power law, with an exponent of about 0.75. There are good reasons for expecting a power law: for example, the body-size-to-body-length relationship follows a power law with an exponent of 0.33, and the body-size-to-surface-area relationship a power law with an exponent of 0.67. The explanation for an exponent of 0.75 is not obvious—however it is worth noting that several physiological variables appear to be related to body size by approximately the same exponent, for example, the basal metabolic rate. This power law formula applies to the "average" brain of mammals taken as a whole, but each family (cats, rodents, primates, etc) departs from it to some degree, in a way that generally reflects the overall "sophistication" of behavior. Primates, for a given body size, have brains 5 to 10 times as large as the formula predicts. Predators tend to have relatively larger brains than the animals they prey on; placental mammals (the great majority) have relatively larger brains than marsupials such as the opossum.
When the mammalian brain increases in size, not all parts increase at the same rate. In particular, the larger the brain of a species, the greater the fraction taken up by the cortex. Thus, in the species with the largest brains, most of their volume is filled with cortex: this applies not only to humans, but also to animals such as dolphins, whales, or elephants.
The evolution of homo sapiens over the past two million years has been marked by a steady increase in brain size, but much of it can be accounted for by corresponding increases in body size. There are, however, many departures from the trend that are difficult to explain in a systematic way: in particular, the appearance of modern man about 100,000 years ago was marked by a decrease in body size at the same time as an increase in brain size. Even so, it is notorious that Neanderthals, which went extinct about 40,000 years ago, had larger brains than modern homo sapiens.
Not all investigators are happy with the amount of attention that has been paid to brain size. Roth and Dicke, for example, have argued that factors other than size are more highly correlated with intelligence, such as the number of cortical neurons and the speed of their connections. Moreover they point out that intelligence depends not just on the amount of brain tissue, but on the details of how it is structured.
This text uses material from Wikipedia, licensed under CC BY-SA