Homology/Analogy

1. Botany 940 Evidence for evolution Homology/Analogy Natalia Alvarez Kevin Coleman 2006

2. Homolog structure: Similar structure and position, but different function Courtesy of Prof. Ken Sytsma Analog structure: Similar function, but different origin http://evolution.berkeley.edu

3. Homology Courtesy of Prof. Ken Sytsma How can we explain this? Hypotheses??

4. Homology • Archetypal explanation “The same organ in different animals under every variety of form and function.”(Owen,1843) • Common ancestry “A structure is similar among related organisms because those organisms have all descended from a common ancestor that had an equivalent trait. “ (Darwin,1859) Homology in character evolution. Staton, July 2000

5. Wells’ Critique: Circular definition Homology/Common ancestor “Features are homologous because they are inherited from a common ancestor” Common ancestry is inferred using homologous features. • Features can be tested by “Multiple ad hoc hypothesis of homology” (Kluge 1997) • Origin of arthropod compound eye. Oakley,2002.

6. How would you test common ancestry?

7. How would you test common ancestry? • Fossil record • Structure and position • behavioral patterns

8. Fossil record -Fossil intermediates • Behavioral patterns Bird Alligator Dinosaur

9. How would you test common ancestry? • Fossil record • Structure and position • behavioral patterns • Genetics

10. Wells’ Critique: Genetics • Assumption: homologous features are programmed by similar genes • Problems 1. Similar genes determine radically different structures. 2. Organisms with different genes produce similar structures. Example: Pax6 in fruit flies, mice and humans

11. http://big.big.or.jp/~mastakeu/pax6.html http://www.umich.edu/~mmgmed/faculty/glaser/glaser2-resprojects.html • Genetics: Homolog structures and genes Is there a correlation between genotype and phenotype? Pax6 in fruit flies, mice and humans: "master regulator of eye development“ (qtd. in Displan,1997). Downstream genes are not the same, thus determines different structures.

12. How would you test common ancestry? • Fossil record • Structure and position • behavioral patterns • Genetics • Developmental pathways

13. Wells’ Critique: Developmental Pathways • Assumption: homologous features should develop in similar ways • Problems 1. Similar pathways may produce very dissimilar features. 2. Similar features are often produced via very different pathways. Haeckel’s drawings Gilbert, S. F. 1997. http://7e.devbio.com/about.php

14. Developmental pathways: shared features, shared early developmental features ,presence and sequence of development stages. http://www.natcenscied.org/icons/icon4haeckel.html

15. How would you test common ancestry? • Fossil record • Structure and position • behavioral patterns • Genetics • Developmental pathways • others?

16. Foquieria – Foquieriaceae North America Allauidia – Didieriaceae Madagascar Analogy • Different structures which perform the same function (Owen, 1843) • Convergence: Similarities between organisms that evolved independently. Tasmanian wolf Mexican wolf

17. Counterarguments • “Convergent evolution is used by evolutionists to explain homologies that do not line up with the evolutionary tree.” • The probability of a beneficial mutation is very low. In addition, the probability of two different organisms with the same configuration from the same mutation is astronomically low.

18. Convergence = directionality? • Oakley and Cunningham 2002

19. -“When you examine the tapestry of evolution you see the same patterns emerging over and over again. Gould's idea of rerunning the tape of life is not hypothetical; it's happening all around us. And the result is well known to biologists — evolutionary convergence. When convergence is the rule, you can rerun the tape of life as often as you like and the outcome will be much the same. Convergence means that life is not only predictable at a basic level; it also has a direction.” (Simon Conway Morris 2002)

20. Design or Mere Accident? • “The mechanism of Darwinism is at last securely founded” and as a consequence “man has to understand that he is a mere accident.” - Jaques Monod, 1970 • Two questions:

21. Design or Mere Accident? • “The mechanism of Darwinism is at last securely founded” and as a consequence “man has to understand that he is a mere accident.” - Jaques Monod, 1970 • Two questions: • Why does a naturalistic mechanism preclude a divine scheme? • Are just men an accident, or are women merely accidental as well?

22. What is the PURPOSE of this seminar??

23. What is the PURPOSE of this seminar?? • Understand evidence for evolution • Allow scientists in different fields the opportunity to discuss their perspectives • Circle the wagons against ID • Critically discuss how we can best communicate “evolution” to a non-technical audience

24. What is the PURPOSE of this seminar?? • Awareness of the limits of science: the full range of the human experience cannot be explain by science alone • Openness to questioning and inquiry, and accepting the possibility of being wrong. • Reverence for life: life is amazing, should we not all be in awe of biodiversity?

25. Evolution vs. ID: Does it matter? If so, why? • How do we stop the current loss of biodiversity? • Is this debate sucking energy away from the crisis at hand? • Can we find common ground and work together toward protecting the planet?