23 - A Brief History of Evolution (w/ Aaron Griffing!)

23. A Brief History of Evolution (w/ Aaron Griffing!)

Survival of the fittest is a famous anecdote but isn’t always the best way of describing natural selection. Who was Charles Darwin? Whose shoulders did he stand on? What is evolution? Let’s learn to be scientifically conversational.


General Learning Concepts

1)    What is the theory of evolution? Where did it come from?

a.    What is a theory? Broad explanations for a wide range of phenomena. They are concise (i.e., generally don't have a long list of exceptions and special rules), coherent, systematic, predictive, and broadly applicable.

i.    In common usage, the word theory means just a hunch, but in science, a theory is a powerful explanation for a broad set of observations. Words with both technical and everyday meanings often cause confusion. Even scientists sometimes use the word theory when they really mean hypothesis or even just a hunch.

b.    What is evolution? Evolution consists of changes in the heritable traits of a population of organisms as successive generations replace one another. It is populations of organisms that evolve, not individual organisms.

i.    Berkley EDU puts it as: Biological evolution, simply put, is descent with modification.

c.     What is evolution responsible for? What isn’t it? Evolution is responsible for the genetic differences observed by descent of organisms. It highlights the importance of genetic variation and the random nature of genetic drift. It helps explain natural selection and differential reproduction, and how different species can co-evolve. It is not responsible for making organisms “better”; rather, more suited to their environments with a range of traits, not even considering evolutionary drift and shift. Evolution does not promote individual evolution, but rather a population. Evolution is not always slow; this can happen more rapidly, especially with microbes. While the catchphrase of natural selection is “survival of the fittest”, this does not mean that less fit organisms cannot survive: some things are fit enough. Finally, not all traits of organisms are a consequence of adaptation; there is a great deal of history that comes along with many organisms. [2]

d.    Charles Darwin: Charles Darwin (1809-1882) is best known for his theories about the evolution of species, which challenged prevailing notions views of evolution. Darwin made his initial observations during his voyage on the H.M.S. Beagle to South America.  His most important data about the variations among species were gathered on the Galapagos Islands off the coast of South America. Returning home with his findings, Darwin spent many years refining his theories about natural selection, at last rushing his book, On the Origin of Species (1851), into print in 1858 when he realized that his colleague Alfred Russel Wallace had arrived independently at very similar conclusions.

e.    Alfred Russell Wallace and others: Darwin had concomitantly discovered evolution with Wallace and disproved a number of pieces of work from Lamarck, and built upon some of Buffon’s original work.

  i.    Georges-Louis Leclerc, Comte de Buffon (1707-1788) was responsible for publication of Histoire Naturelle, an encyclopedia responsible for interpreting the world. He used Isaac Newton’s work to propose the earth could have been formed from comets striking the sun, molten rock cooling to land and clouds raining to form oceans (which he estimated would take 70,000 years, far longer than the young earth generally perceived at the time). He claimed that as the climate cooled, life began dependent on the spaces they were. The minute details at the time seem to all be wrong today, but the milestone truly was that he believed earth had a history.

ii.    Jean Baptiste Pierre Antoine de Monet, Chevalier de Lamarck (1744 – 1829) was a medical doctor (never practiced) turned botanist turned invertebrate biologist. While he died in poverty and obscurity thanks to his radical views, Lamarck is most famous for proposing that there was change in animals through use and disuse and that organisms adapted to their surroundings and became increasingly complex.

iii.    Alfred Russel Wallace (1823-1913) was a man of many talents - an explorer, collector, naturalist, geographer, anthropologist and political commentator. Most famously, he had the revolutionary idea of evolution by natural selection entirely independently of Charles Darwin.

2)    Development of the theory of evolution

a.    Natural section within a species: Technically termed anagenesis; a species adapts to its environment and traits of those who do not survive fade from the species. Observable change is possible to note over time, hundreds of generations later, without branching the species’ evolutionary path.

b.    Natural selection to diverge species: Speciation is when a new, distinct species is created through the course of evolution. This uses natural selection/adaptation and is often noticed in independent populations.

c.     Proper evidence: Darwin used the fossil record to leverage morphology for the theory of evolution. He noted how seemingly related species were in similar places but not necessarily the same places (zebras, finches). Early stages of embryos look (morphologically) very similar.

d.    The Earth’s age: While Darwin was incorrect about the actual age of the planet, he did note (thanks to his son’s calculations and physicist William Thomson / Lord Kelvin) that the planet must be older than 6,000 years to allow for the speciation that was observable in the 18th century.

e.    Further theories: Darwin proposed pangenesis, an incorrect theory that asserted that offspring had traits from both parents because of “gemmules”, or the seeds of cells, produced by all organs and structures from each parent. If there were not enough gemmules, the organism would die. He said that if the offspring more resembled one parent, that parent’s gemmules must be stronger.

3)    Modern day examples of evolution

a.    Molecular examples of evolution: Richard Lenski, at Michigan State University, has worked to show evolution on a molecular scale by founding 12 replicate populations of E. coli from the same ancestor, in the same environments, and allowed them to evolve for 30,000 generations to examine how different populations evolve. The lab can challenge them with competition, analyze their genomes, and measure spontaneous mutation rates.

4)    Fun Tidbits

a.    Alfred Russell Wallace: Spent time on the Amazon in Brazil, but after more than four years collecting his ship caught fire in the Atlantic and sank. He survived and spent eight years in the Singapore region, collecting almost 110,000 insects, 7500 shells, 8050 bird skins, and 410 mammal and reptile specimens, including probably more than 5000 species new to science. [2]

b.    Charles Darwin: Darwin married his first cousin, Emma Wedgwood, having 10 children ove the course of their marriage. He also liked to eat “strange” birds, like owls and hawks. [2]

5)    Solicited Questions

a.    Is evolution real? Yes.

Calvin YeagerComment