2. A History of Evolutionary Thought

There’s over 2,000 years of organized thought and writing regarding evolution - contributions from Greek, Roman, and Islamic scholars

Greek philosopher Aristotle (384–322 BCE) - studied the natural world and published several volumes on animals based on systematic observations

His book History of Animals was one of the first zoological taxonomies ever created

The animals were placed in a hierarchy based on their abilities and modes of reproduction

• Ex. Warm blooded animals ranked above vertebrates

This concept of “higher” and “lower” organisms - Expanded upon by scholars in the Medieval period to form the Scala Naturae (Latin for “ladder of being”)

• This chain of being - had god at that top of the chain of command and minerals at the bottom

• Medieval Christians thought humans were placed closer to god than other species

Aristotle’s works - Rediscovered by Islamic scholars in the ninth century and translated into Arabic, Syriac, Persian - his work influenced others for years to come

Al-Jahiz (776–868 CE) - Author of over 200 books who’s most well known work is the Book of Animals - he described over 350 species in zoological detail

He introduced the idea and mechanisms of biological evolution 1000 years before Darwin proposed the concept of natural selection in 1859

He also brought up how species evolve over time and how environmental factors influence the process

• He brought up these ideas that were later brought up by European scientists in the 19th century

Ibn al-Haytham (965–1040) - A 10th-century Islamic scholar - focused on optics and how human vision works

He came up with using experiments to verify theory - similar to modern scientific method

He discovering the laws of reflection and refraction and inventing the camera obscura (essential for photography)

Scientific method - A method of procedure that has characterized natural science since the 17th century

The Scientific Method was first codified by Francis Bacon (1561–1626)

Francis Bacon - founder of empiricism

Empiricism - The idea that all learning and knowledge derives from experience and observation

John Ray (1627–1705) - an English parson and naturalist - first person to publish a biological definition of species in his Historia Plantarum

He defined a species as a group of morphologically similar organisms arising from a common ancestor

Species - A group of similar organisms capable of producing fertile offspring

Carl von Linne - A Swedish scientist who laid the foundations for the modern scheme of taxonomy used today

He established the system of binomial nomenclature

Binomial nomenclature - A system of classification consisting of two terms: the first identifies the genus to which it belongs, and the second identifies the species

Comte de Buffon (1707–1788), was a prominent French naturalist

He came up with a technique of comparing similar structures across different species - comparative anatomy

Georges Cuvier (1769–1832) - A paleontologist and comparative anatomist

A major contribution he made - finding that some species had become extinct through analyses of large fossil quadrupeds

At the time - They knew that fossils were of older species but they didn’t know that there were no living relatives of fossils

Extinction - interpreted as implying imperfection - suggesting God’s work was flawed (due to the bible)

Cuvier - famous for his ability to reconstruct what an extinct animal looked like from fragmentary remains

Catastrophism - The theory that the Earth’s geology has largely been shaped by sudden, short-lived, violent events, possibly worldwide in scope - compare to uniformitarianism

James Hutton (1726–1797) - “Father of Geology.” Publishes Theory of the Earth and introduces idea of Deep Time

He explains how features of the earth were formed through the actions of rain, wind, rivers, and volcanic eruptions

Uniformitarianism - The theoretical perspective that the geologic processes observed today are the same as the processes operating in the past

Charles Lyell (1797–1875) - Establishes geology as a science based on observation

He published first edition of The Principles of Geology (1830–33) - pushed forward his view on uniformitarianism and the research he found on it

Jean-Baptiste Lamarck (1744–1829) - Publishes theory of the Inheritance of acquired characteristics

He is the first Western scientist to propose a mechanism explaining how traits change in species over time and to recognize the importance of the physical environment in acting on species and their survival

• Lamarck’s theory involved a three-step process

  1. An animal experiencing a radical change in its environment

  2. The animal (either individual or species) responding with a new kind of behaviour

  3. How the behavioural change results in morphological (meaning physical) changes to the animal that are successfully passed on to subsequent generations

Ex. Giraffes actively stretched their necks to reach leaves on tall trees to eat - this was then passed down to their offspring

August Weismann (1834–1914) - Publishes the results of an experiment involving mice - disproving the inheritance of acquired characteristics (Lamarck’s theory)

He amputated the tails of 68 mice - then successively bred five generations of them - all of them had perfectly healthy long tails in spite of having parents whose tails were missing

He also publishes The Germ Plasm - early idea of inheritance through sexual reproduction

Thomas Malthus (1766–1834) - Economist and “Father of Statistics”- publishes An Essay on Population

He introduces concept of carrying capacity based on his observations

Carrying capacity - The amount of organisms that an environment can reliably support

He inspires Darwin’s idea of “natural selection”

Charles Darwin (1809–1882) - Publishes On the Origin of Species by Means of Natural Selection

He collected fossils - found both extant and extinct members of the same species in the same geographic location

• This challenged the theory of catastrophism put forth by Cuvier

He also observed geographic variation in the same species

His observations challenged catastrophism and Fixity of Species

Fixity of Species - The idea that a species, once created, remains unchanged over time

He took another 20 years of data collection after the voyage (aboard the Beagle) to share his conclusions about evolution

Evolution - a descent with modification - species share a common ancestor yet change over time, giving rise to new species

Artificial Selection - Identifying desirable traits in plants and animals - enhancing and perpetuating those traits in future generations

Gregor Mendel (1822–1884) - Publishes experiments in plant hybridization - outlining the fundamentals of genetic inheritance (pea plants)

Phenotypes - The detectable or visible expression of an organism’s genotype

Genes - A sequence of DNA that provides coding information for the construction of proteins

Gene flow - The introduction of new genetic material into a population through interbreeding between two distinct populations

Genetic drift - Random changes in allele frequencies within a population from one generation to the next

Gene pool - The entire collection of genetic material in a breeding community that can be passed from one generation to the next

Microevolution - Changes in gene frequencies between generations within a population

Macroevolution - Longer-term changes in a population that can eventually result in speciation - individuals from different populations are no longer able to successfully interbreed and produce viable offspring

Modern Synthesis - The mid-20th century merging of Mendelian genetics with Darwinian evolution that resulted in a unified theory of evolution

Theodosius Dobzhansky (1900–1975) - One of the founders of the Modern Synthesis of biology and genetics

Publishes Genetics and the Origin of Species - Documents a genetic model of speciation through reproductive isolation

Speciation - The process by which new genetically distinct species evolve from

Urban sprawl - shrinking the availability of wilderness habitats for animals - some animals have adapted to these new environments

Ex. Crested anoles - used to live in forests - now live in towns and cities throughout the Caribbean

Adapted by developing longer limbs and longer toe pads with special scales that allow them to cling to smooth surfaces

Evolution - does not always progress in the same direction over time

Ex. Qikiqtania wakei - originally a fish that evolved to walk on land, then evolved to live back in the water

Natural selection can only act on slight variations in anatomy that are already present

If we could create anatomical structures out of thin air in response to changes in environmental pressures - we would have stronger anterior cruciate ligaments ACLs (they are vulnerable to tearing)

Fitness - An individual’s ability to survive and reproduce viable offspring who also survive and reproduce

Creationism - The belief that the universe and all living organisms originate from specific acts of divine creation

Intelligent design - A pseudoscientific set of beliefs based on the notion that life on earth is so complex - can only have been designed by a supernatural entity

Teaching evolution in the United States has been quite debated since many people believe in other things such as creationism and don’t believe in evolution

As a species - we are still evolving - we still respond to selective pressures biologically

Ex. Human Immunodeficiency Virus (HIV), height, and wisdom teeth

All these traits are heritable - transmitted genetically from generation to generation

They also have variations of the trait within the population and the trait - they are successfully reproduced