Lecture 1 Anthropology 153 : Introduction to Physical/Evolutionary Anthropology ( Human Biology and Evolution) Charles Darwin : ( https://www.britannica.com/biography/Charles-Darwin ; https://www.youtube.com/watch?v=-NFfSLlCawE ; https://www.youtube.com/watch?v=-NFfSLlCawE ; https://iep.utm.edu/darwin/ )

Charles Darwin’s law or theory of evolution has two main parts. Most people who know of Darwin’s law are familiar with his idea of 1) NATURAL SELECTION. ( https://en.wikipedia.org/wiki/Natural_selection )

However, Darwin also found that 2) ALL LIFE IS RELATED TO ALL OTHER LIFE THROUGH COMMON ANCESTRAL SPECIES. This is the principle of PHYLOGENY as represented by a “THE TREE OF LIFE” diagram. ( https://en.wikipedia.org/wiki/Tree_of_life_(biology) )

Darwin lacked good theories of 1) what the mechanism of heredity was by which traits could be passed on from one generation to the next ; and 2) how variation in a species arose .

Darwin’s successors solved theoretical problem 1) with the discovery of genes and DNA ; and 2) with the discovery of genetic mutations. These theories combined with Darwin’s theories of Phylogenetic Tree of Life and Natural Selection form the Modern Evolutionary Synthesis.

(https://en.wikipedia.org/wiki/Evolution : https://en.wikipedia.org/wiki/Modern_synthesis_(20th_century )

IMPORTANTLY, THE MEASURE OF DARWINIAN FITNESS/SUCCESSFUL ADAPTATION IS SPECIES POPULATION GROWTH; THE MEASURE OF UNFITNESS IS POPULATION SHRINKING , THE ULTIMATE UNFITNESS IS EXTINCTION.

The Darwinian Tree of Life represents COMMON ANCESTORAL relations between different species at nodes of branching on the Tree diagram ( see handout of Primate Order section of Tree of Life).The Tree of Life diagram implies a timeline from bottom to top. Thereby it represents EVOLUTION by NATURAL SELECTION of new traits and retention of some old traits.

The primate order is an order of the mammal class. All primates are mammals ; not all mammals are primates; increasingly inclusive categories as we go down on the Tree of Life . (see handouts on Evolution and Tree of Life)

It was Darwin’s claim that all life is related through common ancestral species INCLUDING HUMANS (!) that was controversial (not so much natural selection), because it conflicted with the Christian doctrine of human origin by God’s creation in the Garden of Eden.

The idea that humans had evolved out of an earlier ancestor AT ALL was controversial. Darwin specifically hypothesized that the living species with the closest back in time or fewest generations back to a common ancestor with humans are chimpanzees; and that humans originated in Africa. Subsequently, scientists explored parts of Africa looking for fossil remains evidence of a so-called MISSING LINK species. The idea is links in a chain as representing a line of species , one link ascending from the previous links. The “missing link” would connect humans to our common ancestor on the Tree of Life with chimps.

A fossil with characteristics constituting a link between a human “link” and a chimp “link” was discovered by Raymond Dart in Southern Africa (page 291 of text) ; and subsequently by many others . This proved Darwin’s hypothesis true. Dart found a fossil with a chimp sized brain BUT BI-PEDAL, OR HABITUALLY WALKING ON TWO FEET INSTEAD OF FOUR (quadrapedal). The phylogenetic-Tree of Life classification term for habitually bi-pedal primates is HOMININ.

( https://www.britannica.com/biography/Raymond-A-Dart )

Scientific Cosmology

The modern scientific method of finding out truths about the world, the universe, originated 500 to 600 years ago in Europe. It has produced the estimates of the time of origin of major events of natural history of interest to this class as listed on the Timeline handout.

The origin of life on Earth was approximately 3.6 billion years ago. The first life forms or species were single celled and cloned to reproduce. Cloning means an organism makes a copy of itself to produce the next generation. The origin of sexually reproducing species was approximately 1.2 billion years ago. Reproduction is necessary to perpetuate species because individual organisms are mortal. Dinosaurs’ origin approximately 240 million years ago and extinction 65 million years ago is an example of Darwin’s principle of NATURAL SELECTION against. There were other mass extinctions prior to the dinosaur (many different species) mass extinction.

( https://www.britannica.com/science/life/Evolution-and-the-history-of-life-on-Earth )

The dinosaur extinction was (an example of Darwin’s concept of species being selected against) probably due to a comet or meteor striking and exploding like many , many nuclear bombs on the earth ; and throwing so much debris up into the atmosphere that it blocked much of the sun’s light for many, many years; and thereby killing much plant life that was the food of the dinosaurs. (https://www.britannica.com/animal/dinosaur/Extinction )

Mammals ( we are mammals) lived simultaneously with dinosaurs. They were small , furry animals relative to dinosaurs, and the reduced amount of plant food was enough for their smaller bodies to survive the loss of plant life. Thus, mammals were SELECTED FOR in the Darwinian sense. Mammals were fit relative to dinosaurs; survival of the fit species.

( What Happened Immediately After the Dinosaurs Went Extinct ? Mammals ! https://www.youtube.com/watch?v=c7nyan0wnkQ )

Three characteristic traits of mammals are ,1) mammary glands to feed the young, 2) warmblood ,3) bodily fur. ( https://en.wikipedia.org/wiki/Mammal )

Primates, A PHYLOGENETIC ORDER OF MAMMALS, retain these traits; and primates evolved stereoscopic vision (page 138 of text) as an adaptation to living in trees. This is not to be confused with the Tree of Life metaphor ; primates actually did live in trees. Stereoscopic vision, by way of eyes in front of the head forming almost parallel lines of sight , gives sharper vision at a distance. Thereby, primates didn’t fall of the trees to death , and could catch insects more exactly; in other words adaptation in the trees. (Chapter 7 of the text ; https://www.youtube.com/watch?v=BpnlS_ach-0 What is a Primate?)

HOMININS

Hominins (See last section of Chapter 12 and Chapters 13, 14 and 15 of the text _Physical Anthropology_) are distinguished from other primates by a skeleton adapted for bipedalism – the habit of _walking_ upright on the two hind limbs. Hominins in this class are habitually, anatomically, physiologically, naturally UPRIGHT-ERECT, BIPEDAL primates . Although, other primate species are able to stand on two legs temporarily , only hominins evolved as habitually bipeds. Kangaroos, some birds and other animals are bipeds , but they are not primates.

https://www.britannica.com/science/bipedalism

Some closely related primate species , including chimpanzees and gorillas, exhibit knuckle walking a pattern of movement in which long arms and the knuckles of the hand support the weight.

See handouts 1 and 2.

There are several Darwinian natural selection hypotheses for the origin of bipedalism evolving out of a quadrupedal/knuckle-walking species ancestral to hominin species.

1) Adaptation to savanna ecological niche: Bipedalism may have allowed primates to move about more freely within savanna environments (grassland, with scattered trees, prevalent in Africa) and to watch out for predators over the tall grasses. Erect bipeds walk greater distance using less energy than quadrupeds can and , with their eyes elevated higher than quadrupeds can see over grasses and see a longer way into the distance for predators or prey. However, evidence from recent fossil finds suggests that early bipedal hominins lived in forested areas.

2) Bipedalism lessens stress from the extreme heat of the savanna in East and Southern Africa. The air is slightly cooler off the ground, and erect bipedalism exposes less surface area of the body to the midday sun.( page 311 of the text)

3) Carrying behavior: Bipedalism allows hominins to carry objects in the two front limbs (arms), enabling the carrying of food and easier transportation of the young ( fleeing predators or pursuing a nomad-migratory life way). Bipedalism also frees hands to carry tools and weapons. This Professor Brown’s football sports example.

4) The genitalia of both sexes are exposed to vision more in erect posture than in quadrupedal stooped posture. This may have resulted in more fertile matings by erect phenotype individuals (see page 311 text)

5) Other primates have free hands while stationary, so the main abilities that hominins have over quadrupedal and knuckle walking primates is that forelimbs-hands are free during locomotion walking over running. However, hands free virtually all the time probably contributed to the evolution of the hands into highly developed organs of manipulation (literally) that are better for the manufacture of tools or for affectionate stroking.

6) Hominin Species

The details of the hominin Tree of Life (“family tree”) are still being developed, but anthropologists generally agree about the primary ancestral relationships of and among hominin species.

1) The lines leading to chimpanzees, m gorillas and humans are believed to have diverged sometime between 8 – 5 million years ago.

2) Fossils of the earliest hominins , from about 7 -1.8 million years ago have been found SOLEY IN AFRICA ( See discussion of Piltdown Hoax on _fake_fossils found in England).

3) Paleoanthropologists generally agree that there were more than one line of hominin species, only one of which evolved into the human or Genus Homo species. The robust australopithecines , which coexisted with early species of the Genus Homo, are not considered ancestral to humans and became extinct approximately 1 million years ago.

( https://www.britannica.com/topic/hominin )

( https://www.youtube.com/watch?v=K3n370ww3L4 Hominin Evolution, Part 1: The First 5 Million Years )

( https://www.amnh.org/explore/videos/exhibits/seven-million-years-human-evolution )