Biological Anthropology

“Lucy” (Australopithecus afarensis)

Biological Anthropology •  The study of the biology and evolution of the morphological and

behavioral traits of humans and their close relatives •  A materialist and scientific view of humans, related species, genes,

bodies, and “minds,” as well as the things they produce, such as artifacts, features, physiological processes, culture, thought, social relationships, societies, technology, etc.

•  Materialism: all things are made of matter, and you can understand all things by referring to their physical (or assumed physical) features (including the mind and thoughts/behaviors generated by the mind)

•  The mind is the unmoved mover (Aristotle) •  “I think therefore I am” Descartes •  Interesting philosophical and cognitive issues here…

•  Science: systematic, evidence-based testing of hypotheses that are based on theories and corroborative evidence

•  “To measure is to know”: quantified data are essential to science

Organisms’ Components •  Organism = a living thing •  Generally all can be sorted into 5 (or 6) kingdoms: animals,

plants, fungi, bacteria, protists •  Materialism: living things are made of matter •  What kind of matter? Molecules…

–  Protein: the stuff living things are made of, e.g., collagen, enzymes, etc.); *there are some exceptions—take upper division biology classes if you are interested

–  Also made of: water, carbohydrates, fats, vitamins/minerals, DNA (nucleic acids), etc.

–  Proteins are long molecules that are folded over on themselves –  The components of protein molecules are smaller molecules called amino

acids (AAs)

Amino Acids •  There are 20 kinds of AAs that make up all

the proteins that organisms have –  alanine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine,

glycine, proline, serine, tyrosine, (essentials:) arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine

•  AAs are made of limited elements: Hydrogen, Oxygen, Nitrogen, Carbon, and Sulfur (S only in methionine and cysteine)

Amino Acids •  AAs are small molecules, but when strung up and folded over on

themselves to form a protein, they can be quite large •  AAs are attached by peptide bonds

Amino acid ‘strand’

Each AA is like a bead on a necklace; electrochemical interactions among neighboring AAs cause the strand to fold over on itself in specific ways. The folded strand is a protein. Different AA sequences will make different proteins.

Protein

•  Proteins interact with other substances (including other proteins) in specific ways that are determined by their electrochemical properties.

•  There are only 20AAs out there—a finite number (though in actuality the story is more complex than this)

•  Different lengths and permutations of the AAs that make up AA strands can lead to countless varieties of proteins

Protein Functions •  Structural proteins (collagen in skin, keratin in hair

and nails, proteins that make up muscle tissue, etc.) •  Transport proteins (hemoglobin is a blood cell protein

that transports oxygen to body tissues) •  Enzymes: proteins that catalyze (speed up) chemical

reactions in the body •  Immune functions •  Signaling functions: E.g., neurons in your brain

communicate with each other; these neurons are proteins (and other substances)

Proteins

•  From where to organisms get the AAs needed for body maintenance and growth?

Food! •  Foods are typically living

(or formerly living) substances…

•  What substances are in our food?

Lichtenstein 1962 “Meat”

Organismic Components •  Organism = a living thing •  Protein: the stuff living things are made of, including

structural proteins like collagen, enzymes, etc.); *there are some exceptions, e.g., viruses--but they are not relevant to our simplified introductory discussion in this class--take upper division biology classes if you are interested

•  Also water, carbohydrates, fats, vitamins/minerals, DNA (nucleic acids), etc.

•  Proteins are long molecules that folded over on themselves

•  The components of protein molecules are smaller molecules called amino acids (AAs)

Organismic Components •  Organism = a living thing •  Protein: the stuff living things are made of, including

structural proteins like collagen, enzymes, etc.); *there are some exceptions, e.g., viruses--but they are not relevant to our simplified introductory discussion in this class--take upper division biology classes if you are interested

•  Also water, carbohydrates, fats, vitamins/minerals, DNA (nucleic acids), etc.

•  Proteins are long molecules that are folded over on themselves

•  The components of protein molecules are smaller molecules called amino acids (AAs)

Proteins to AAs •  We eat proteins, such as a bite of steak (or tofu) •  As a cow muscle tissue, the steak contains a lot of proteins (and other things: fats,

pesticides…)

•  The proteins are cow muscle proteins •  Your body is made of human muscle protein, hair protein, cornea protein,

various neural proteins, etc. •  Cow muscle protein is different from human hair protein; how does the

transformation happen? •  Answer: your digestive system breaks down the cow muscle protein into its

constituent AAs, that is, the amino acids that it is made of (20 possible) •  Those AA molecules are the raw material that is used to build the proteins

your body needs; they get restrung up into new “YOUR HAIR” proteins •  But how do they get restrung up into YOUR HAIR proteins?

Amino Acids to Proteins

…genes

Genes to Proteins •  Protein synthesis •  An elegant process…that we will not go over in this

class •  Upshot: the sequence of nucleotides in DNA

determines the sequence of AAs in protein manufacture (nucleic acid sequence maps to AA sequence, but not one-to-one, and redundancy is built into the system)

•  In other words, your DNA determines what proteins get built out of the AAs that your body extracts from the foreign proteins you eat

•  Genes determine what proteins get built from those raw AA molecules •  Genes are protein-coding units of DNA •  You eat proteins of other living things, and break the protein into amino

acids; then, genes in your DNA re-string those amino acids into proteins that YOU need to survive and reproduce

•  Bodies are made of proteins (fat and carbs and water are essentially there to service these proteins)

•  Genes also code for enyzmes, which are proteins that regulate everything, including development

•  Other parts of DNA do not code for proteins, and have either no function (e.g. “hitchhiker DNA), or function for self-regulation, and other tasks—take advanced biology classes to learn about these very cool things DNA does

•  What’s DNA?

Genes Proteins

DNA •  DeoxyriboNucleic Acid •  A long molecule with a small number of constituent molecules •  Shape is a “double helix”—think of a ladder that is twisted

DNA •  A sugar-phosphate

“backbone,” (I.e., the “sides” of the ladder), and “rungs” are made up of paired nucleic acids

•  There are 4 nucleic acids: adenine (A), thymine (T), cytosine (C), and guanine (G)

•  Note these are not AAs •  A only bonds to T •  C only bonds to G •  A-T and C-G bonds are weak •  Sugar-phosphate bonds are

strong •  Lots of “zipping” action

Genes Proteins Bodies

DNA molecule

Protein

Cell parts, cells, and tissues

Amino acid molecules

Amino acid strand

Organ Body

+

•  Genes are protein-coding regions of an organism’s DNA •  (1) They direct protein synthesis •  (2) They “replicate,” or reproduce, over generations, as they

are passed from parents to offspring (offspring inherit their parents’ genes) –  (a) in single-celled organisms, one “parental” cell’s genes double

then divide and are passed on to two “offspring” cells (the parent cell no longer exists—its body’s proteins now make up the bodies of two offspring)

–  (b) in multicelled organisms, there are two kinds of cells: somatic cells and germ cells:

•  (i) somatic cells (such as human skin cells), live only as a part of the parental body; somatic cell genes build proteins for the parent’s body; reproduction of somatic cells involves gene replication, but the new cells remain a part of the parental body

•  (ii) germ cells (such as sperm and eggs) are housed in the parental body; then, at the time of reproduction, a germ cell leaves the parental body, and develops a new multicelled body of its own

•  THE point: only germ cell genes can make it into the next generation for multicelled organisms like humans

freshwater paramecium (single-celled)

red-tailed hawk (multicelluled)

Genes (DNA segments)

Reproduction in Single vs. Multi-celled Organisms

single-celled “parent”

½ of reproduced genes passed to each of two identical, single-celled “offspring”

multi-celled “parent”

*The somatic line cells ARE the germ line cells

Somatic line cells

Germ line cell

All genes reproduce by doubling

At reproduction, germ line cell leaves prent’s body and multiplies, creating new somatic cells for it’s offspring’s body, and, at some point, a germ line cell (or cells) that the offspring can transmit into the next generation

Germ line cell…

multi-celled “offspring”

•  Heritable genes are passed from parent to offspring over generations

•  Evolution is change in gene frequencies in a population over generations

•  E.g., the genes building proteins for nonbipedality decreased in the human lineage, and the genes for bipedality have increased in the human lineage over evolutionary time

“Evolution”

Natural Selection •  One type of evolution (there are 4 types in total)

whereby a change in gene frequencies in a population over generations happens due to the CAUSAL effects those genes have on reproduction

•  This produces adaptations: parts of organisms like eyes, hearts, camouflage, etc., that are useful in to reproducing in a particular environmental niche.

Assumption 1: Reproducing entities exist.

Natural Selection

Assumption 2: Variations exist, and they can be passed on to offspring (heritable variation).

Natural Selection

Assumption 3: Variations have reproductive consequences in particular environmental niches (e.g., a predator and green surroundings).

Natural Selection

Result: over time, the entire population will come to possess the reproductively superior variation.

Natural Selection

Natural Selection After thousands of generations…

Refinement of traits that facilitate survival and reproduction

Darwin’s Short Definition of NS

“I have called this principle, by which each slight variation [in a trait], if useful, is preserved, by the term Natural Selection.”

- From The Origin of Species

•  Darwin was the first person to discover and describe natural selection, but he did so absent a knowledge of genetics. Darwin was influenced by: –  Recent advances in geology –  An understanding of the significance of within-species

competition –  Artificial selection –  Comparative anatomy –  Naturalistic studies with colleagues while at university –  Recent advances in paleontology (fossils) –  Geographic distribution of traits in different environments

Darwin’s thought processes leading to his discovery of natural selection

(absent a knowledge of genetics)…

...Natural Selection

Our definition for this class

•  Natural selection is change in gene frequencies in a population over generations due to the causal effects genes have on reproduction

Exercise

•  Genes for eyecolor frequencies example (in this class?)

•  Changes over generations •  Causal and noncausal…

– Sun damages them – They’re unattractive – Random falling off a cliff

Issues with and Misunderstandings about Evolution

•  Many exist, and historically they have even had abominable impacts on human lives

•  Many misconceptions involve lacking relevant background knowledge about biology

•  Many involve trying to tie evolutionary principles to moralistic frameworks

•  Many involve challenges that materialist, evolutionary accounts might pose to deeply-held beliefs in nonmaterial accounts of life

•  In academia, many involve challenges to deeply-held assumptions about “nature vs. nurture”

•  These are beyond the scope of this class, but… •  At least one misunderstanding can be traced to the problematic

phrase “survival of the fittest”…

“Survival of the Fittest” •  A phrase introduced by H. Spencer in the 1800s to justify the oppression of so-called

inferior populations; based on a misinterpretation of Darwin’s theory of natural selection; caused a LOT of horrible acts in human history

•  Problematic terms and meanings: –  Survival? Nope, it is actually reproduction that is relevant--salmon die to spawn; birth kills 1/100

women in regions without access to medical care; men risk their lives in fights over women; male praying mantises are eaten alive by the female during copulation

–  What does “fittest” mean? The strongest? The fastest? What about the rodent-like mongrels that survived the meteor that killed off the dinosaurs 65 million years ago?

–  Fittest? Fittest what? Fittest species? Fittest group? Fittest individual? Fittest genes? Fittest ecosystem?

–  Better: “reproduction of the best reproducers”? That’s useless too… •  Typically, laypeople think the phrase explains why certain species dominate other

species, and justifies the painful suffering we see endured by weaker organisms to the benefit of stronger organisms: e.g., when we see a gazelle get hunted and eaten by a cheetah (cheetahs being the more "fit” species), we say “that is nature’s way—survival of the fittest”; additionally we see and justify the suffering of within-species conflict “that guy won the fight, thus ‘ survival of the fittest’” No!!!

•  This is NOT a moral thing. It is just a way to try to understand why the organisms we can observe have the features they do. Period.

•  Keep in mind the following tale…

The Bear and the Campers

Our Tale

•  Between-species issues (esp. who-eats-who) matters, but…

•  Within-species competition is an extremely important and underrepresented factor in understanding how natural selection works!

A final point re. intro to genetics and natural selection: mutations

•  From where do these heritable variations originate?

•  Mutations. •  What are mutations?

–  Nucleotide substitutions (an AGT or C gets replaced by the ‘wrong letter’)

•  The impact of mutations when they are on somatic-line cells vs. germ lines

•  Mutations impact evolution in different ways based on what types of cells they are in

–  Somatic cell = maybe cancer—bad for survival, but questionably bad; and may or may not impact reproduction—or not cancer (thus irrelevant to survival/reproduction)

–  Germ line = Potentially very important to reproduction (not survival) and NS

–  Examples