Primates Chock Lecture Notes

Chapter 6: Why are we the only Primates who choke on food? – An evolutionary trade-off. o Chimps have a large mouth, take in more food. When they swallow, the chimp’s epiglottis automatically closes off the trachea preventing it from ever choking. o Humans still have a soft palate and epiglottis, our mouth is much smaller, we have a different diet (meat) and our jaws and tongue ar.se smealcle.r. .At. rest there is a space between the soft palate and epiglottis. This means that when we ingest food, there is a potential risk of it entering our trachea. Our body has evolved a method where the epiglottis will usually close off the trachea, but sometimes it fails to happen. Evolution of speech: unique to humans o If you replace the space for propagation of sound in the chimpanzee, you have a short vertical tube and a long horizontal tube. o In humans you have a long vertical and horizontal tube that are about the same size. In humans the tube is connected to the nervous system which communicates with our brain. The vertical tube allows humans to say vowels and constants that chimps can’t say. o From on evolutionary perspective, our ability to communicate far out ways the disadvantages of a high probability of choking on food. Studying Adaptations: o The initial function of fins was to stabilize the fish body in its environment; it is an adaptation. o In terrestrial animals (tetrapod’s), the limbs (that have evolved from fins) are used to support the body in an aerial environment. The limbs of tetrapod’s are thus an exaptation for terrestrial mobility (locomotion). o Exaptation: adaptation whose current function is not the one for which the structure initially evolved. Essentially, you recycled one structure and used it to preform another function. o The coelacanth discovery was the same type of discovery as discovering a dinosaur. They have limbs instead of fins. Hair evolution – adaptation or exaptation to conserve heat? o Elephant experiment: extinct elephants had very thick coats of hair, but today of their body have unique features, such as the head with a round shape and big eyes, a snout that sticks out, two ears on top of the head and another pair next to it. They have four limbs - two front ones called hands and two back ones known as feet. Their fingers are long and flexible with nails at the end. The skin on their body is soft while they walk using only their back limbs which make them look like they are hopping. they don't use clothes but just wear some simple accessories like hats the body hairs of these characters vary in color from black to white These creatures walk by standing on two feet in an upright manner similar to us humans A few parts of their bodies have hair-like things including eyebrows, eyelashes, beards or whiskers. their skin is smooth without much fuzziness When walking around, these creatures usually move slowly using both front hands together at once - instead of alternating between each hand and foot step like we do when we walk uprightly (bi-pedal). This makes them look more funny because they sort of wobble while moving forward. their way of walking makes it appear as if they are hopping or bouncing along because only use back limbs for movement of the elephant are thinned skinned. These hot spots allow the elephant to lose heat and regulate their temperature. Why do they still have some hair on elephants though? o The pin theory suggests that if you put a source of heat underneath a plate without pins, the plate on the pins will conserve heat better. o Initial adaptation may have been for losing heat, but now its purpose is more about heat preservation (exaptation). Additionally, hair was originally used for sensory structures. Feathers: adaptation or exaptation for flight? o Why would the first feather come up? - New discoveries suggest that dinosaurs had feathers. There is still controversy as to how dinosaurs were able to produce heat, so there is no definitive answer. Potentially the dinosaurs simply desired to maintain warmth (which produce its own heat, it needs a method to hold that heat as proficiently as possible, a coat made of feathers (or fur) is a solution that has consistently been preferred by evolution. o Some dinosaurs had feathers on tails sexual selection? o Feathers are an example of an exaptation for flight. Evolution of the loss of fur and skin colour in humans: o 6-7 million years ago, the hominines (all human species) shared a common ancestor with the chimpanzee (pale skin covered of a dark fur). o Lucy or Australopithecus afarensis (remember) is an example of a primitive species. At one point the diversity of human species was quite high. o Looking at the cranium and teeth can provide insight on the human species. o Crest in skull meant a very large temporal muscle. Large teeth indicated they ate large food. Front teeth on upper jaw were very small – more recent human species. Older species had longer teeth because they were better for eating fruit. A. afarensis o Tropical forests o Bipedal and arboreal o Diet of fruits, tubers and leaves o Sedentary way of life o Lived in a environment with extensive tropical forests, so temperature was quite cordial, lived much of its existence in trees trying to eat fruits from there. As of 3 Myr: o Important cooling o Droughts in East Africa o Formation of savannas o Impact on hominin species o Humans lived on fruits, easy access to water. The cooling climate led to the human species living in more open habitats, rather than the forests. This led to evolution. Homo ergaster (=H.erectus) (1,2 Myr): o Less fruit available; meat added to the diet. o Walks longer distances for prey and water. o Adapt to life on the plains o More active lifestyle (hunter-gatherer) o Open habitat - availability of food was not so high and moving around around became more important. As a result, the morphology of humans changed – longer legs and arms. Water is also less abundant in more open areas.