Isabella Rotman Response Questions FM 2

>> RESPONSE QUESTIONS #5    (posted on the course blog by Tuesday, noon)

1 - In Wonderful Life Gould hypothesizes on cultural values, assumptions, and what kind of logic are evident in the original interpretation of the Burgess Shale, and then the change in thinking that led to its recent re-interpretation. What model of biodiversity and evolutionary change does Gould argue resulted in the earlier error in classifying the Burgess Shale animals? What is the original cultural/historical source of that model, or what he calls “iconography”?

Gould explains that for too long we have been thinking of evolution as a chain, a series of steps leading upwards to the pinnacle of existence. Each link in the chain was an improvement, and all the proceeded it simply existed to bring the peak to light. Because of this, the fossils of the Burgess Shale were categorized to fit into modern groups. Walcott viewed all of the Burgess Fauna as ancestral versions of the improved forms they would later evolve into. I believe human beings felt this way because we are intrinsically self centered, believing we are the pinnacle of something. If we cant be made in God’s image, then we must at least be the most evolved animal. This idea is supported by earlier ideas of evolution, by which animals evolved into primates, then Neanderthal, then man, then through the races of man, ending with Caucasians. Clearly this was hypothesized by Caucasians. I feel it illustrates the idea well.

 I found this quote particularly amazing. It refers to human reaction to learning that the earth is very old, and Homo Sapiens are very new.

“We cannot bear the central implication of this brave new world. If humanity arose just yesterday on a small twig of one branch of a flourishing tree, then life may not, in any genuine sense, exist for us or because of us. Perhaps we are just an afterthought, a kind of accident, just one bauble on the Christmas tree of evolution.”

2 - Notice that much of Gould’s argument centers on discussing evolutionary tress (phylogenies) of the kind you constructed on a small scale.                   At the end of the chapter we see he is interested in the overall shapes (“topology”) of the phylogenies. Why? What does he claim that the shape of phylogenies imply about how evolution happens over long stretches of time that had been neglected by biologists? What kinds of causal factors alter the course of evolution, the shape of phylogenies, and the eventual designs of organisms that we see today?

What we know now is that evolution is not a cone, or a Christmas tree.  Gould believes that evolution involves many species adapting over time, branching out into twigs, and at the same time going extinct. Some move on to diversify and others stop at certain points.  Gould says “We live surrounded by coeval twigs of life’s tree. In Darwin’s world, all (as survivors in a tough game) has some claim on equal status. Why, then, do we usually choose to construct a ranking of implied worth (by assuming complexity, or relative nearness to humans, for example)?”

Gould gives the example of a bush with branching twigs because these twigs end at different levels (lines of evolution going extinct) and branch off at irregular intervals (multiple species diverging from comment ancestry). Bushes can also take many shapes, which could show a line of evolution going in different directions, or changing in size as species go extinct or diverge.

2b - Related: What does it mean to “replay the Tape of Life” and why is this an interesting idea to Gould? Relate Gould’s preferred model with the views of early Catastrophists – what would Cuvier (if alive) like and not like about Gould’s interpretation?

Gould goes farther in saying that who goes extinct and who continues to evolve is not completely based of competence. Species may have an edge, yes, but much of evolution is unpredictable, based on natural disasters or changes in climate. If the tape was replayed the results would have been extremely different. This is Gould’s hypothesis. I believe it is relevant but not completely true. Animals survive because they are adaptable. A more adaptable species will survive environmental change better than a very specialized species. This will have some effect even when we replay the tape/

3 - What is “disparity” versus “diversity”? Give an original example (one not given in the reading).

Diversity refers to number of species. It also refers to difference in body plans.  Gould redefines disparity to oly mean number as species, such as: Bats have a high diversity because there are many bat species.  There are not nearly as many species of anteaters, so anteaters have a lower diversity. The term disparity is therefore reserved for number of body plans. An environment such as a coral reef has a high disparity, because it is home to many different phylum.

 4 - In the reading Evolution by Walking what is so interesting about how the American Museum of Natural History has changed their mammal display? Why is it significant in how we think about biodiversity in his opinion?

The American Museum changed the organization of their mammal display to walk through evolution at it’s “branching off” points. Most museum exhibits of the past have displayed specimens canonically. This method shows life’s history in a linear form, starting with the ‘old’ and ending with homo sapiens. Maybe the specimens increase with complexity, or perhaps they are set up in accordance with time, but they are always in a straight line. Linear, a path towards the peak, which is usually man. The Natural History museum did something much more interesting when they redid the mammal display. The animals are arranged by when they branched off, not my their later success. Groups that branched early (like marsupials, because they are pre-placental) are in the beginning of the hall, while animals that branched later at the end. The hall does not end with human beings, but manatees. Changes that happened along one branch of the tree, and not where the branch meets the trunk, such as increased brain size in humans, are not relevant in this form of organization.