Darwinism (Externalism): From Environment to Organism

Characteristics of Darwinian Evolutionary Theory: The Arrow that Runs from Environment to Organism

Darwinian theory is an externalist system. Outside factors (environments) produce internal changes in organisms. Environment instructs us but over generations by selection rather than instruction from birth as in Locke's tabula rasa.

1) Evolution is any systematic change over time and applies to Chevies as much as to beetles. In principle, mutation is random and any feature can be made by selection. Evolution is gradual and happens over very long intervals in living species. (Life is about 3.6 billion years old, human lineages are about 200,000. (Zimmer compares the relative time of man and of life to a firefly's blink at the end of a summer day.) We last shared a mother with chimpanzees 5-7 mya (million years ago).

2) New, unstable niches (r-selection) and those with many predators are associated with rapidly breeding, shorter lived, smaller individuals who give minimum parental investment. As with soldiers in war, displays of rank are few. Stable niches (K selection) and those with few predators fill to their limit: individuals tend to be larger, live longer, have fewer children but invest in them more, and make cooperative networks.

3) Diversity: 15,000 species (4 of 5 animals!) of nematode worms. 400 different microbes live in your mouth. There are 10,000-20,000 species of ants and 300,000 of beetles. Life thrives in different forms from +300 degrees F to colonies that live in spots of dust in glaciers (Wilson, 2002). The centers of species variation lie along the equator in South America, Africa, and SE Asia. Move north or south and life becomes plainer.

The number of species is a function of connected geographic area. Cut an existing area in half and the largest species die first. (It's not always good to be at the top of the food chain.) Domains shrink as function of HIPPO (habitat destruction, invaders, pollution, human population, overharvesting)(Wilson, 2002).

4) Species: a troublesome concept even when it's not applied to humans. Species were originally defined as organisms that cannot reproduce together. Next, as organisms that do not usually reproduce together (on basis of preference or of separation). We now find that camels and llamas (apart for 13 million years) produce viable young who can themselves reproduce.

5) Species originate in genetic variation, perpetuated by geographic separation, founder effects (unique traits of the first creatures to arrive in a new setting), and extreme duress. Speciation is also pushed by duplication of entire genes that take up new functions and by epigenetic effects from mothers who can sometimes turn a gene off for several generations before another mother turns it back on.
Sexual selection (see below) also increases diversity (whatever a guy's oddities, if he's clever, kind, and resourceful, women will admire him and other men will imitate him). Mating preferences can change in a generation. (Saltacid spiders born of forced matings will mate with each other but reject members of their parental species who also reject them.) Also environmental stress (heat, cold, radiation, starvation, drought) increases heritable variation through Hsp-90s that release the expression of mutations instead of hiding it. Species may also result from changes in the relative timing of maturation in different developmental systems (heterochrony).

6) Natural selection: Variation, inheritance, and differential reproduction crafted "fitness" and many (uncountable) psychological adaptations.

7) Fitness is another controversial term. It usually refers to longevity and number of offspring reared to maturity. (It has no relevance to moral superiority or to social entitlement. May be applied to a gene, organism, individual, or in rare circumstances, a group (Keller & Lloyd, 1992).

8) Adaptations are a nest of behaviors and structures that solve a survival problem. For example, an apple has many features that fit together and lead to new apple trees. Thus, adaptations specify a survival goal and lead us to group traits by their relevance to that goal. Adaptations are efficient and seen in every normal individual of a species.

9) Psychological adaptations are usually easy to learn, fun to do, and seen in every normal member of a species (Miller, 1999). Natural selection, guided by environmental pressures, reduces differences between individuals. "Tooth and claw" and "selfish genes." "Mismatch" between our culture and our nature accounts for many discomforts.

10) Similarities between different species are a function of convergence (Similar environments make similar traits emerge from different origins.) Similarities between different species are also a function of homology (similar genes produced different structures that led to different niches).

11) We are crafted to survive through child rearing. Many of us died in childbirth or from disease, combat, and accidents by age 30. Selection, therefore, did not operate on our characteristics that develop after age 40.

12) Sexual selection occurs in the environment of our mate's eye: competition within each gender and between males and females magnify small differences between contestants. The average for a trait increases with each generation. Mate preferences magnify preferences of earlier ones; thus, SS is a recursive process that enhances small variations and makes gender-specific displays that appear at courtship and advertise reproductive assets.

13) Natural selection makes individuals more similar as they strive to achieve a better fit to their environment. NS limits the range of SS because displays are, by definition, metabolically and reproductively expensive, disproportionate to survival needs, and make their carrier a prominent target. (e.g., NFL helmets could well have flashing lights and tall plumes except for survival costs such as fewer goals and getting killed by opposing players. No goals, no cheerleaders.). Displays can lead to extinction if environments change drastically.

Sexual selection can drive culture in animals and humans. Human displays include: music, painting, poetry, novels and essays, sports, comedy, ridicule, expensive watches, pocket rocket cars, and the jokes we tell. (They also include skyscrapers.) Legislation, the tax code, and medical research also sprouted from survival interests but grew and grew and still grow every time another ambitious hominid joins the contest. Geoff Miller is convinced that sexual selection "drove" the evolution of human intelligence.1 Mate choices would be influenced by social success in many different activities. I think he's partially correct.

14) Natural and sexual selection lead to arms races (Red Queen effects) between predator and prey, males and females of any species, plants and insects, and organisms and environments. Whatever one player achieves a gain, the second compensates.

Notes & Refs:

Wilson, E. O. (2002) The Future of Life. NY: Knopf. See also Wilson, E.O. (1992) The Diversity of Life Cambridge, MA; Harvard.
Wilson, E. O. (2002) The Future of Life. NY: Knopf.
Keller and Lloyd (1992) Keywords in Evolutionary Biology and Dawkins, R. (1982) The Extended Phenotype. NY: Oxford, review some of "Fitness" difficulties. A-L Barabasi (2002) Linked, uses "fitness" as a property of nodes: the more links and the more rapidly a node acquires links, the greater its fitness.
Miller, G. (1999) Human Language and Intelligence as Sexually Selected Fitness Indicators. Presentation given at the Hunter School of Social Work, Manhattan, NY, 4/14/99.

Copyright 2002, all rights reserved, James Brody

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