Anthro lab 4 - lab 4 PDF

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Panagiota Stathopoulou Instructor: Jonathan Fallas Anthropology 105: 1L01 May 16th, 2020 Lab 4: Life History Introduction Life history can be defined as “The strategy an organism uses to allocate its energy towards growth, maintenance, reproduction, raising offspring to independence, and avoiding death.” Bogin and Smith (2000). Life history varies among different species, such as among humans, other hominins, apes and other primates. There have been relationships discovered between body mass, brain size, and life history variables. These variables are related among humans, apes and other primates. In primate history, the larger the body mass of the primate, the more delayed the age of first reproduction will be. Additionally, the larger the body mass among primate history, the longer the lifespan. Lastly, the larger the body mass, the larger the brain size. Humans have the highest age of first reproduction compared to other hominins, apes and other primates. Humans have the longest lifespan compared to other hominins, apes and other primates. Humans also have the largest encephalization quotient compared to other hominins, apes and other primates. In these variables, fossil hominins have a lower age of first reproduction compared to humans, but relatively higher age compared to apes and other primates. Fossil hominins have a lower lifespan than humans and relatively higher than apes and other primates. Additionally fossil hominins have a lower EQ than humans, yet higher than apes and other primates. In this project, we investigated how and when the human-like pattern of large brains, long growth periods, and long maximum lifespans evolved by examining these traits in fossil hominins.

Hypotheses 1. I expect age at first reproduction in Australopithecus, Homo habilis, Homo erectus, and Neanderthals to be similar to each other, around 10 years old and way lower compared to humans. I expect it to be higher, compared to other primates. I expect Neanderthals to be most similar to humans in terms of age at first reproduction. 2. I expect max lifespan in Australopithecus, Homo habilis, Homo erectus, and Neanderthals to be similar to each other, around 40 years old and way lower compared to humans. I expect it to be higher, compared to other primates. I expect Neanderthals to be most similar to humans in terms of max lifespan. 3. I expect encephalization quotient in Australopithecus, Homo habilis, Homo erectus, and Neanderthals to be lower compared to humans, around half the value. I expect it to be higher, compared to other primates. I expect Neanderthals to be most similar to humans in terms of encephalization quotient.

Methods In our lab project, the data was provided to us for use. However, the way that the data was gathered is as follows. Different orbital and cranial measurements were taken of 3 Australopithecus, 3 Homo habilis, 3 Homo erectus, 3 Neanderthals. These measurements were taken with a tool called a caliper. The types of measurements taken were orbital height, cranial height, cranial width, and cranial length. The orbital height was used to estimate the approximate body mass in kilograms of the species with a specific logarithmic equation and was taken with a Vernier caliper. The cranial measurements were used to estimate the approximate brain size of the species and were taken using an outside caliper. The orbital height measurements as well as the cranial measurements were taken in millimeters. The three scatterplots that were provided to us include equations. With these equations for the relationships, they were able to use the body mass measurements to estimate age at first reproduction (in years), maximum lifespan (in years) as well as expected brain size. The observed brain size values (cc) were the same as the first values gathered from the cranial measurements. Next the encephalization quotient is a ratio that was determined by dividing the observed brain size values by the expected brain size values.

Results According to our results, my hypotheses were correct. From figure 1 we can see that age of first reproduction among humans was the highest, at around 20 years old. The next highest value was around 11 years old for Neanderthals. Australopithecus, Homo Habilis, Homo erectus and apes were similar to each other in that they ranged from 8-9 years old. The other primates displayed a very young age of first reproduction ranging from2 to almost 4 years old. Additionally, in figure 2 we can see that maximum lifespan was highest among humans, averaging around 85 years old. Next highest lifespan was Neanderthals at around 46 years old. Australopithecus, Homo habilis, Homo erectus and apes were similar to each other ranging from 40-43 years old while other primates had the lowest max lifespans ranging from 20-25 years old. Lastly, in figure three we can see that the encephalization quotient of humans was the highest at 3.08. Neanderthals came next at 2.1. Australopithecus, Homo habilis, Homo erectus were most similar to each other around an EQ of 2, while apes and other primates were ranging around an EQ of 1. Our results support my hypotheses.

Discussion Our results in this study relate to the larger issue of how and when human-like pattern of large brains, long growth periods, and long maximum lifespans evolved in the hominin group. It is apparent that humans are different from other hominins, apes and primates in the way that they have the biggest brains, have a longer lifespan, and display the longest life history. The relationships between body mass, life history, and brain size are all connected. As body mass goes up, so does life history and brain size. From the data, it is shown that the primates that are mainly, insectivores display relatively smaller brain sizes while primates that are mainly frugivores display relatively bigger brain sizes. This suggests that diet plays a big role in brain size as well as other life factors. One major issue that all studies investigating fossil species is the dependence on estimates. Often times we are not able to measure the variable that we are interested in especially if that species is extinct. Instead, we need to derive estimates from fossils and skeletal variables. Having said that, a lot of error may lay within these parameters. Humans are unique among other hominins in that they are still alive, and the data gathered from them is observed rather than estimated. This makes us question the accuracy of the results gathered from the data about other hominins. Humans are also outliers within the graphs in comparison to the other species. Additionally, the relationships between body mass and age at first reproduction as well as body mass and life history are not as useful because it does not capture that extended period of growth and extended lifespan that is required. Within Microsoft excel, we used formulas to come up with the estimations for hominins. We didn’t use that for humans since the results were observed and there was no need for estimation. However, if we were to follow the same formula to get the human values, they would be way different and not as accurate which make us question the accuracy for the rest of the data. By looking at the EQ of these species, the relative brain size for the fossil hominins can aid us in reconstructing their life histories considering that EQ is more accurate compared to the other data. Perhaps other forms of analysis and other forms of research should be used to evaluate life history traits in hominins for more accuracy and credible results.

Figures

Avg. age at first reproduction Age (years)

25.00 20.00 15.00 10.00 5.00

Ha pl or hi ne s St re ps irh in e

Ap es

Hu m Au an st s ra lop ith ec us Ho m o ha bil is Ho m o er ec tu s Ne an de rth als

0.00

Species

Figure 1: This figure shows the average age at first reproduction among different species.

Ha pl or hi ne s St re ps irh in e

Ap es

90.00 80.00 70.00 60.00 50.00 40.00 30.00 20.00 10.00 0.00

Hu m Au an st s ra lop ith ec us Ho m o ha bil is Ho m o er ec tu s Ne an de rth als

Age (years)

Avg Maximum Lifespan

Species

Figure 2: This figure shows the average maximum lifespan of different species.

Ha pl or hi ne s St re ps irh in e

Ap es

3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00

Hu m an Au s st ra lop ith ec us Ho m o ha bil is Ho m o er ec tu s Ne an de rth als

EQ

Avg Encephilization quotient

Species

Figure 3: This figure shows the average encephalization quotient among different species....