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Small, Big-Brained Animals Dodge Extinction
ananyo writes "Large-brained animals may be less likely to go extinct in a changing world, perhaps because they can use their greater intelligence to adapt their behavior to new conditions, according to an analysis presented to a meeting of conservation biologists this week. Plotting brain size against body size creates a tidy curve. But some species have bigger or smaller brains than the curve would predict for their body size. And a bigger brain-to-body-size ratio usually means a smarter animal. The researchers looked at the sizes of such deviations from the curve and their relationships to the fates of two groups of mammalian species — 'palaeo' and 'modern'. Analysis of each group produced similar results: species that weighed less than 10 kilograms and had big brains for their body size were less likely to have gone extinct or be placed on the International Union for Conservation of Nature red list for endangered species. For species larger than about 10 kilograms, the advantage of having a large brain seems to be swamped by the disadvantage of being big — such as attracting the unwelcome attention of humans."
m(brain)/m(body) is used as a rough estimate of intelligence in animals. The encaphalization ratio, which is what is used in TFA, is more precise, but harder to calculate. Both of them is rough enough to only work for comparisons between species, not between individuals within the same species.
A Modest Porpoisal
You have to look at it in aggregate the way the study is. Groups of individuals wiped out in natural disasters are just that individuals. Humans survive those disasters because our big brains have enabled large populations of us to live outside what might be considered our most natural habitat. That geographic diversity has protected us as a species from natural disasters.
Your fish example is kinda the same issue. No individual fish however smart is going to be able to cope with the lake going totally dry. However smarter fish might be able to last longer in a lake with changing ecology and shrinking size, during a severe drought, and therefore survive until the rains come. While other species in the lake might die out.
A fish might migrate to a new lake when they are joined by floods. When they separate again a smarter fish species might be better equipped to adapt to the environment of the new lake, colonizing it successfully where other species might have failed. That might enable it to survive as a species even after the first lake dries up.
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All these species, chicken, cows, pigs, etc are afflicted by one of the most deadly parasites of the species Homo sapiens. This is a slow acting cunning parasite, that allows the animals to reproduce before killing them. Thus they never develop an immunity to this parasite.
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
RELATIVE brain size is closely correlated with intelligence - not absolute brain size. The brain size of a whale is MUCH larger than yours, but that is because it has a lot more body to regulate. Dolphins have larger brains than humans and much larger than chimps, and while they obviously have some intelligence, there is no evidence that they are more intelligent than humans or chimps.
Take a look at sharks: they got massive brains, comparable to mammals of similar sizes, and were able to survive mostly unchanged for 450 million years. That's older than land animals exist.
The lasers provide a survival advantage.
I think I had snake once, and it was really quite tasty. I don't know which kind it was, or indeed if it really was a snake. The idea of snake farming is rather amusing though, especially if there's a risk/reward factor there. Is there a golden taste-to-poison ratio?
While there are many species of venomous snakes there are vey few species of poisonous ones. Many kinds of snake venom can be ingested. The venom will not kill you (unless you have a wound in your mouth) but it may make you throw up. That's why you can suck snake venom from a wound without dying yourself.
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Actually, there's a "popular" opinion among paleontologists now that a lot of the dinosaurs were warm blooded, or something like it. So that's not a sufficient explanation. Size was probably a much bigger factor, which is part of what this whole study was about. When times are good, being large helps you out-compete others. When times are hard, like after an asteroid strike or while a particular large-brain mammal is busy destroying the planet, being small makes it easier to hide and lets you get by on less food.
And pointing out that in the real world trends don't continue on infinitely isn't really contributing anything unless you've got at least a theory, and preferably some kind of experiment, to establish where exactly those boundaries are. Just shouting "Being small and big-brained is good, but if you get too small then you don't have any room for a brain!" or "Being large is good, but if you get too large the square-cube law means you won't be able to move!" doesn't contribute a great deal.
But even so, we're rather large ourselves. If we kill off ourselves but don't manage to kill off all other life on the planet, it's quite likely that we'll take most of the other large animals with us, but quite a number of small large-brained animals will survive. (Rats in particular strike me as being pretty good survivors.) So the theory _still_ holds.
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Penalty! Invalid politicization of scientific debate - five minutes in the penalty box!
Actualy the important bit is that brain burns a lot of energy which is why we don't see smart animals everywhere. Given similar body weight, having more of that weight occupied by brain means that the animal has evolved with greater importance of inteligence (larger brain needs more energy) but just because inteligence is more imporant compared to other similaranimals doesn't mean there's more of it than a larger animal would have. Anyway, the point stands - inteligence helps to survive, at least as long as you don't become too big to evaid the best killing machine on Earth - fully armed and trained hordes of Homo Sapiens Sapiens.
Shark brains are tiny, but their distributed nervous system is perhaps more autonomous and substantial than mammalian ones. I've had a dogfish (small Atlantic shark) wiggle off the cutting board and swim away well after I had head and gutted it. When you eat their fresh meat it squirms when you bite it. Mako has a significantly bigger brain than a blue shark, but they're both much smaller than a deer's brain.
"The ability to delude yourself may be an important survival tool" - Jane Wagner -
Neanderthals and a number of other extinct early hominids had brain sizes of 1600cc to 2200cc. Modern homo homo sapiens have a brain size of around 1200cc to 1500cc. Einstein's brain was around 1250cc. Sharks are the most enduring vertebrate on Earth, and have one of the lowest brain/body mass ratios. There's plenty of evidence to refute the premise.
Marris in her Nature article is implying that large brain/body ratios increase species survival likelyhood, based on comparing a "primitive" class of mammals to a "modern" one. But it could just as well be their digestive system was more adaptable, superior immune systems, etc. She started with a theoretical classification of living and extinct mammals (paleo and modern) and tried to support her theory that one has a survival advantage. This is trying to make the empirical data fit the theoretical model, and is crummy science. If one were actually interested in extinction, they should study different species and why they went extinct or not, and then build a theory based on those empirical results.
"The ability to delude yourself may be an important survival tool" - Jane Wagner -
Do NOT cut and suck. Cutting into the bite site can damage underlying organs, increase the risk of infection, and sucking on the bite site does not result in venom removal.
Incising (cutting) and suctioning the bite area has not been shown to be beneficial, but a venom extractor (found in commercial snake bite kits) may be helpful if it is applied to the area within five minutes of the bite and left in place for 30 minutes. A 2004 study of mock venom extraction using a suction device, however, questioned the validity of venom extractors and suggested that their use is unlikely to be effective.
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