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With food poisoning you can straight out tell them what is wrong and you will get sympathy in return.Tell them you are feeling down and all you'll probably get is a 'well cheer up, it can't be that bad'.Does that mean that birds and bats are more closely related to one another than to mice and crocodiles? When we examine bird wings and bat wings closely, we see that there are some major differences.Bat wings consist of flaps of skin stretched between the bones of the fingers and arm.These toolkits last until at least 50,000 to 28,000 years ago.In Africa, the Middle Stone Age toolkits sometimes include blades and other types of archeological evidence (beads and artifacts that indicate the use of color and symbols) that are typical of the Upper Paleolithic in Europe.Between about 400,000 and 200,000 years ago, the pace of innovation in stone technology began to accelerate very slightly.By the beginning of this time, handaxes were made with exquisite craftsmanship, and eventually gave way to smaller, more diverse toolkits, with an emphasis on One of the main innovations was the application of ‘prepared core technique,’ in which a core was carefully flaked on one side so that for a flake of predetermined size and shape could be produced in a single blow.
Birds, bats, mice, and crocodiles all have four limbs. The ancestor of tetrapods evolved four limbs, and its descendents have inherited that feature so the presence of four limbs is a homology. For example, birds and bats both have wings, while mice and crocodiles do not.This idea is illustrated by the phylogeny below, which is based on a large number of other characters.Bird and bat wings are analogous that is, they have separate evolutionary origins, but are superficially similar because they have both experienced natural selection that shaped them to play a key role in flight. Interestingly, though bird and bat wings are analogous as wings, as forelimbs they are homologous.Bird wings consist of feathers extending all along the arm.These structural dissimilarities suggest that bird wings and bat wings were not inherited from a common ancestor with wings.