Evolution at Arcadia

Week 6: Evolution

Lecture

Evolution is descent with modification, which consists of slow change in species over many generations

Natural selection is the survival and reproduction of individuals due to differences in phenotype

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Mutation is a change in the DNA that can be passed down to the individual’s children

Genetic drift is random change in the frequencies of genetic variation, which causes change in a population but does not produce adaptations

Gene flow is the migration of a population and their genetic information to another place

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Anthropologists study evolution of humans and their closest relatives as well as cultural evolution. We are mainly interested in human evolution and that of our relatives.


Activity 1: Mutation Telephone

Starting with the instructor, a simple message sent through the line. There will be significant change in the message as it is passed along. This change happened from an accumulation of small mistakes the students made, much like mutations happen in DNA. Eventually, after enough time passes, those small mistakes add up to be large adaptations. These adaptations can even create new species that do not resemble the original species if enough mutations happen.

The first round of the game I said: “We love Halloween at Arcadia” and after being repeated 20 times, it ended as “We aren’t awkward”.

The second round of the game I said: “I am very excited for Thanksgiving break” and after being repeated 20 times, the sentence was basically inaudible, but close to “I want to shhhhhh”.


Activity 2: Adaptive Monsters

Students got ready for Halloween by making monsters! The students could create any kind of monster they wanted, but they had to be adapted for a certain landscape (Tundra, Jungle, and Under the Sea).

The students determined some important adaptations for each environment – 

Tundra: The ability to pick up short grass, ability to walk on hard ground for long periods of time, and ability to withstand cold weather

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[Clan leader creation]

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[This monster has wings to fly, claws to rip prey apart, spikes to shoot prey, and a thick coat to stay warm.]

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[This monster has large teeth to eat and defend with, a large tail that smashes through the rough ground, and multiple layers of fur to stay warm.]

Jungle: The ability to climb, tails to maintain balance and run through trees, and nocturnal site.

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[Clan leader creation]

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[This monster has a long tail for balancing, multiple legs to run fast, and many snake heads to defend itself.]

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[This monster grows bananas and throws them in defense. It is able to attract its prey by DJing on its record player.]

Under the Sea: Gills to breathe, large teeth to eat and defend, tails or fins to move

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[Clan leader creation]

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[This monster is able to glow in the dark. It moves throughout the water using tentacles. It has large teeth to destroy its prey.]

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[This monster can electrocute others with its tentacles. It has many, many eyes that helps it see in the dark.]


Ending Thoughts

The students really enjoyed both activities. After completing “Mutation Telephone”, I went through the circle to determine where mistakes (or ‘mutations’) had been made. Students giggled as they confessed they couldn’t hear the person in front of them, so they just mumbled something instead. I pointed out that if evolution, these mutations happen over millions of years, and are passed down from generation to generation; until there is a different species entirely.

I was pleased with how intuitive and smart the children’s monsters were. They took time to understand their assigned landscape and put great effort into designing a species that would be adapted for the unique challenges it would face. Those who were preparing to live in a tundra all designed monsters with thick, heavy coats of fur. Every monster who had to survive living in the sea had gills to breathe. They also had tails, tentacles, or fins to allow them to move under water. The jungle monsters had claws to climb up trees and long tails to stabilize them.

Teaching evolution is challenging in any setting, but especially to young students… and especially in the south. Due to inadequate education standards, students receive poor evolution education here. Evolution is described as “only a theory”, with no further explanation that scientific theories are fact. Because of this, I was extremely nervous about presenting the lecture. I was concerned the students would have no previous understanding of the concept – or even been told evolution is a lie.

I am pleased to say I was completely wrong! Multiple students knew that evolution meant “change over time” before I began. Those who did not seemed to really grasp the basics of micro-evolution after the mutation game. I was even more impressed with how appropriately adapted the monsters were to their specific landscapes. Students asked cunning questions about why certain species are better adapted for certain environments, then others. It gave me an excellent opportunity to discuss macro-evolution.

Week 8: Comparative Osteology

Physical anthropologists rely on osteology, or the scientific study of bones, to identify individual species, learn about the lives of an individual, or even to identify ancient illnesses (aka paleopathology). The skeletal features of bones reflect the life histories of individuals, and trained osteologists can use those features to identify the age, sex, diet, and, at times, even the cause of death of a particular specimen.

However, analyzing and comparing the bones from different species can also tell us about the evolutionary history of those species and the degree to which different species are related. For example, the overall form and organization of a dog’s skeletal features would be very similar to those of wolves, as those species are related. The same could be said for different species of fish, reptiles, turtles, etc.

In anthropology, osteologists often compare human skeletons with those of other primates so that we can learn about our ancient human past. In today’s activity, our TMSE students compared cranial features of human, chimpanzee, and coyote skulls, to learn about cranial capacity, dental formulas, diet, and the overall degree of similarity among species. For this activity, students were encouraged to think about the similarities and differences between each of the individual specimens. If they are similar, what makes them similar? If they are different, then how could we explain those differences in an evolutionary context?

To begin with, the students compared the skeletal characteristics of human, chimpanzee, and coyote skulls. Students were able to identify the human skull and distinguish it from the chimpanzee skull rather quickly, but additional analysis was needed to characterize precisely why the students thought they were so different.

skulls

The human chimpanzee skulls differed, for example, in the size of the teeth, the size of the cranium, and even the shape of the skull itself. Students also learned a new term, prognathism, to describe the degree to which the facial features extend out from the face. Chimpanzees are definitely more prognathic than humans, as are coyotes. However, the human and chimpanzee skulls were more similar to each other than they were to the coyote, which had a completely different structure.

 

In seeking a better way to describe the possible differences and similarities, we then analyzed two key features on each skull: teeth and cranial size.

To analyze the similarity in dentition, students were asked to come up with the dental formula for each specimen. A dental formula is essentially a count of the different types of teeth for a specimen, beginning with incisors (cutting teeth in the front of the mouth), canines (teeth for slashing), premolars (for stabilizing food and for grinding); and molars (grinders).

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By counting the tooth types for the human, chimpanzee, and coyote skulls, our TMSE students figured out that humans and chimpanzees have the exact same dental formula! However, coyotes have a different formula.

Our students quickly ascertained that this similarity is likely due to the fact that humans and chimpanzees are related, both as primates and by our shared evolutionary past.

 

To continue to address some of these differences, we then compared the size of the cavity that houses the brain, also known as the cranial capacity.

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By comparing across species, our students figured out that humans have the largest brain, followed by the chimpanzee, and then the coyote. After a lively discussion of the brain size of dolphins, humans, dinosaurs, and dogs, we reached the conclusion that our human brains are MASSIVE relative to our body size. Which, of course, means that we are intelligent creatures.

Our comparative analysis led us to hypothesize that the dental formula and cranial capacity may help determine whether a particular specimen is related to humans or not. To test out our theory, we then threw an unknown skull into the mix. After figuring out the dental formula, describing the tooth size, and looking at the cranial characteristics, our students concluded that the unknown skull was, in fact, related to humans because it shared a dental formula and had a cranial capacity that was in between that of the human and of the chimpanzees.

As it turns out, our students were absolutely correct! The unknown skull was Australopithecus afarensis, one of our evolutionary ancestors.

This activity ended up being a lot of fun, as everyone got a chance to handle castes of skulls and learn about how physical anthropologists may characterize skeletons. Moreover, by learning about basic skeletal features and interspecies variation, our students were able to conduct a comparative analysis of those features and to critically analyze the results based on that analysis.

All in all, a great day!

 

The lesson plan for this activity can be downloaded here.

Week 8 Skeletal Features