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Increase inhominin brain sizeTask: Use the P-R-O strategy to construct a theory-based explanation for puzzling problem: Refer to the handout you received in lecture...

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Increase inhominin brain sizeTask: Use the P-R-O strategy to construct a theory-based explanation for puzzling problem: Refer to the handout you received in lecture to complete this assignment: The handout is also available on Canvas under Lecture Materials Puzzling Problem (P):Homo sapiens has the largest brain size (relative to body size) of any mammal: This increase happened quite recently; in the genus Homo The graph shows the brain sizes of Sahelanthropus, an ape that lived close to the tim

Increase inhominin brain size Task: Use the P-R-O strategy to construct a theory-based explanation for puzzling problem: Refer to the handout you received in lecture to complete this assignment: The handout is also available on Canvas under Lecture Materials Puzzling Problem (P): Homo sapiens has the largest brain size (relative to body size) of any mammal: This increase happened quite recently; in the genus Homo The graph shows the brain sizes of Sahelanthropus, an ape that lived close to the time that hominin and chimpanzee lineages split, Australopithecus; and four species of Homo: Homo habilis; Homo erectus; Homo neanderthalensis, and Homo sapiens. During the evolutionary history of hominins_ tnere was behavioral change: hominins began to cook their food. There were also structural changes: decrease in jaw muscle size and strength and an increase in brain size_ Reasoning steps (R) Guiding questions: 1. Which came frst; cooking or decrease in jaw muscle size and strength? Justify your answer by considering how the conditions for natural selection favoring decrease in jaw muscle size and strength would have been met in an early population in the genus Homo. 2. How did both cooking and decrease in jaw muscle strength change the conditions for natural selection; leading to the evolution of increased brain size in the genus Homo? Outcome (O) 3. Based on this case study; explain one of the following_ Aleading cause of fire deaths in young children is accidental fires set by the child. Hint: Consider why children are so fascinated by fire. Why might this behavior have been adaptive in our ancestors? Most mammals are terrified of fire. Two exceptions are dogs and cats,who often curlup in front of fireplaces: Hint: Humans have domesticated many animals, but dogs and cats are the most likely to be pets and to share our homes: Consider the role that selection played the process of domestication: Unlike earlier hominins, Homo erectus made nests and slept € on the ground, instead of in trees Hint: Why did early hominins build nests and sleep in trees instead of on the ground? What dangers do they avoid? What allowed Homo erectus to sleep on the ground instead of in trees; despite these dangers?



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(Hard.) Does the psychological environment affect the anatomy of the brain? This question was studied experimentally by Mark Rosenzweig and his associates. 20 The subjects for the study came from a genetically pure strain of rats. From each litter, one rat was selected at random for the treatment group, and one for the control group. Both groups got exactly the same kind of food and drink - as much as they wanted. But each animal in the treatment group lived with 11 others in a large cage, furnished with playthings which were changed daily. Animals in the control group lived in isolation, with no toys. After a
month, the experimental animals were killed and dissected. On the average, the control animals were heavier and had heavier brains, perhaps because they ate more and got less exercise. However, " the itreatment group had consistently heavier cortexes (the "grey matter;" or thinking part of the brain). This experiment was repeated many times; results from the first 5 trials are shown in the table: "T" means treatment, and "C" is for control. Each line refers to one pair of animals. In the first pair, the animal in treatment had a cortex weighing 689 milligrams; the one in control had a lighter cortex, weighing only 657 milligrams. And so on. Two methods of analyzing the data will be presented in the form of exercises. Both methods take into account the pairing, which is a crucial feature of the data. (The pairing comes from randomization within litter.)
(a) First analysis. How many paire there in all? In how many of these pairs did the treatment animal have a heavier cortex? Suppose treatment had no effect, so each animal of the pair had a $50-50$ chance to have the heavier cortex, independently from pair to pair. Under this assumption, how likely is it that an investigator would get as many pairs as Rosenzweig did, or more, with the treatment animal having the heavier cortex? What do you infer?
(b) Second analysis. For each pair of animals, compute the difference in cortex weights "treatment - control"." Find the average and SD of all these differences. The null hypothesis says that these differences are like draws made at random with replacement from a box whose average is $0-$ the treatment has no effect. Make a z-test of this hypothesis. What do you infer?
(c) To ensure the validity of the analysis, the following precaution was taken. "The brain dissection and analysis of each set of littermates was done in immediate succession but in a random order and identified only by code number so that the person doing the dissection does not know which cage the rat comes from." Comment briefly on the following: What was the point of this precaution? Was it a good idea?

Today, we're going to be discussing another evolutionary change, and that is brain development. So we know that the Earth looks and functions tremendously different millions of years ago than it does now. So that means our early ancestors to humans had to develop along with that change. So that meant that brain size did, too. From what we saw, we know that larger brains, we're more favored over smaller ones, and this meant that the costs did not outweigh the benefits. So let's look at some costs and benefits of having a larger brain. We know there are maintenance costs, energy costs and developmental costs, but the benefits are things like increased in cognitive abilities. So things like over time and more sophisticated way of having thoughts and expression and tool making. So we can hypothesize them that because natural selection favored a larger brain to that of a smaller brain, that then those benefits outweighed the costs. And this led or could lead to things like survival and the chance of having a better meat. So at the top in the middle here we were given 14 points to graph and these air 14 different birds, so the ex access is our deviation from expected brain size, and our Y access is our mortality. So let's quickly get a graph set up here. All right. Our first point is negative, 2.4, and that is with mortality rate of nine. We have negative 2.1 mortality rate of 0.7. We have negative. 2.22 point five, I mean, sorry. 2.5 negative 1.82 point nine negative 12.4 2.7 0.32 Point eight 0.72 point four, 1.22 point eight, 1.32 point three yeah, to 2.6, 2.32 point six, 3.2 point three and three point to 2.6. Let's just put a trend line here. Okay? So what we want to infer then, is what is this deviation of brain sized mortality? Say, since we see the trend line is getting lower immortality as brain size gets bigger. We then can infer that adult mortality tends to be lower in birds with a larger brain size

Hi, everyone. Here it is. Given the cross section of cortical bone. Mhm. 4.8 into 10 to the power minus four. You can be square. Mask of the men is 70 kg pencil. Sprint is 100 into 10 to the power six nuclear per meter square in the first part because due to inside and upset diameter of humor, the region of cortical wound will increase Mhm mm, by a factor. 10. So our new becomes are into paint. So area new becomes Why are and to 20 square that is Hyundai. Mm. Right. Okay, that is 100 into 4.8 into 10 to the par minus four. Uh huh. Nutrition. Yeah, No second part. Mhm. The worry of the men will increase mhm, mhm by affected to an inch in each dimension. Yeah. Mm. So new volume building can chew into volume authorities. Yeah. Mhm. Yeah. No. Yeah. Yeah. March of old men upon the order Mars of new men. Oh, my substitute. The value mass of old men is 70. Behold mass of new men. We are finding mm people. So that is a mass of Newman. You will get 70,000 kitchens. Yeah, no new went after men. Yeah. 70,000 and 29.8. That is 6.86 10 to the power five Newton. So rejecting is press. Okay? Mhm. Yeah. Okay. 6.86 10 to the power five upon 4.8. 10 to the par minus two. So it is to be 1.43 trying to give our seven Newton parameters square. Mm. No friction of right and pencil. Sprint. Yeah. Sprint off. Human a ball inside of strength. 1.43 10 to the power seven back on hundreds. So it is to me 0.143 14.3%. There. So All right. Mhm. Yeah. No. Yeah. Thanks for watching it.

All right. We have some data and we have the the MRI values is the explanatory variable. And the I. Q. Is response variable and we want to find the least squares regression line and I use this uh spreadsheet program to do that for me and how I did that. Just highlight the data. And then you go to insert chart which is right in here, insert chart and then you get some options and then you basically see this and you can select what do you want scatter diagram, some other lines, whatever you want there. And then to get the line you go down to series, you have to select trend line and then you might need to go down here where it says label. You have to click use equation. And that is the trend line that's the least squares regression line. And what do you notice about the value of the slope. Look at that thing, it's super close to 2.86 times 10 to the negative five. That's uh for all intents and purposes for most humans that's gonna be zero. But it's not exactly zero. So it's technically not zero. But it's it's very very close to zero. Which means that this is actually rather horizontal line very close to the 20. And this seems to fit. Because if we're looking at this data it's it's kind of linear, but at the same time it's very flat. It's like it means it as one variable goes up, the other variable doesn't go up by much. It looks like it because we've scaled in. Um But then if you look at the correlation coefficient are here and I mean it's equals corral for the correlation coefficient here, it's like the data. Yeah. And we see this value .54. So that's the linear correlation coefficient. So kind of makes sense that it's it's kind of it's it goes in a line, but at the same time there's still quite a bit of scatter. And so when we're looking at the scatter plot and we see the linear correlation coefficient, this seems like a reasonable result that this data doesn't really show or that that the correlation between these two variables is not uh not that much pretty low, not correlated at all for all intensive purposes. Uh And so when there is no relation between the explanatory response variables, we just use the mean of the white make prediction. So Yeah. Yeah. I mean, which in this spreadsheet program is average? Was average, get your data And it's 136.4. And so what that means is we're going to take the average and that's what the MRI that's the of anybody. So the average IQ predicted like an individual whose recounts a million and whose MRI candace 830,000? Well 136.4. Which 136.4 is going to be roughly here. And if you can imagine drawn the line here straight across, which would actually kind of fit with the data, is just very mhm horizontal, looking at the horizon. If we zoom out, so there you go.

This question is discussing how a couple decades ago we didn't have as many fossils as we have now in that it was originally hypothesized that large, human sized brains I probably evolved before at the same time with my pet out. Hi Pedialyte E. And so the question is, now that we have a bunch of fossils, what do the fossil? So, which came first? It's going to be large brains or by Pedialyte E. So our ardipithecus ramidus had relatively small brain. However, it walked upright and it left by 4.4 million years ago. And this is the first one that we know of, or at least at the textbook mentions that at least appeared to be walking up right. Do you think Sal Anthropocene, which is about six million years old, has evidence is walking upright, But the book mentions this one. Now there is a discussion on if Ardipithecus or Ardipithecus ramidus was actually an ancestor of humans or something separate. But as of right now, we're going to say it was at least similar looking to our ancestors and then the same with the next one, Homer Rudolph finances once again, some people argue this shouldn't be a and the genus Homo should be in different genus. It wasn't actual ancestor, etcetera, etcetera. But Homer Rudolph Fences. That's when we see the bigger brain enough. But it was walking. I misspoke. That's when I see the bigger brain. But they lived about 1.85 million years ago up until home lower doll fences, and I think it was Homo habilis. The brain cases were about the same size and about as big as a check. So looking at these two, the first walking upright and then the first bigger brain, the Ardipithecus ramidus is going to be, um, bipedal evolved first from the fossils that we currently have.


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