ANTH110-006

9/3 ?? Modern Human Biological Diversity Human Genetic Diversity Ancient Genes - Genetically humans have not had fundamental changes for over hundred thousands of years when anatomically modern humans emerged - Up until 10,000 years ago, our ancestors were foraging (hunting and gathering) for survival *Remember from previous notes there are only 5 foragers left. With the advent of agriculture and the domestication of animals, human populations began to suffer from “diseases of civilization” which include: - Atherosclerosis (hardening of the arteries) - Diabetes - Cancer - Hypertension - Emphysema - Obesity (not a surprise in todays society!) Human Genetics: Genetics research and the resulting potential medical advances constitute a revolution sweeping the study of humans both modern and ancient populations. Begun formally in 1990, the U.S. Human Genome Project was an effort coordinated by the U.S. Department of Energy and the National Institutes of Health. Polymorphic - The modern human is POLYMORPHIC which means the species gene pool has alternative forms or alleles for particular genes. - This translated into alternative phenotypic traits, such as brown vs. blue eyes, darker vs. lighter skin (depending on how much melanoma your body needs: how much time does your culture spend outside: how long are the days or nights?) - Alleles: alternative forms of the same gene Eye Color: A Polymorphic Trait: The once-held view that blue eye color is a simple recessive is wrong. The genetics of eye colors are so complex that almost any parent-child combination of eye colors can occur. (The graph shows Not Mendelian Genetics) Mutation: a change in the DNA sequence that produces an altered gene. (The majority of mutations are thought to occur because of occasional mismatching of the chemical bases that make up DNA) - Polymorphism results from a mutation, which is one source of variation - The other is GENETIC RECOMBINATION Example of a mutation Blue Eyes: The mutation probably emerged in a single individual around the Black Sea region 6,000- 10,000 years ago. Blue eyes are found in parts of Africa, Asia, in particular the northern areas of India. Pakistan and Iran also have large populations of blue eyed people. Heterochromia: when someone has two completely different colored eyes, (ex: one blue eye and one green eye) this can be the result of mutation or injury. Adaptation: The process whereby different genes increase or decrease an organisms chances of survival and reproduction. Natural selection results in more favorable genes becoming more frequent in a population. (ONLY THE STRONG SURVIVE! Ha) Natural selection: The main process that increases the frequency of adaptive traits through time. Example: In 1850, a black moth was spotted for the FIRST time in Manchester, England. By 1950, 95% of moths were black in industrial parts of England. The moths were originally lighter to match the bark on the trees and hide from predators, However when tree bark started to turn black from industrial pollutants the moths adapted and changed to the color of the bark to survive. 9/5 Types of Selection -Directional Selection: (like the moths) a type of natural selection that increases the frequency of a trait -Normalizing Selection: natural selection removes the extremes (ex: babys weight, you cannot give birth to a child that is 30 pounds!) -Balancing Selection: when a heterozygous (varied) combination of genes is favored and the homozygous (same) is not. Polytypic - The human species is also polytypic, that is, the observed frequencies of polymorphic traits very between population around the world - One reason why population in different parts of the world look different - Polytypism is a result from evolutionary processes Human Polytypism: results from two kinds of evolutionary Processes - Humans colonized nearly all habitable regions of the world during the Pleistocene and Holocene (starting around 160,000 years ago) - As a result, these populations became geographically isolated, and to varying degrees, reproductively isolated - Subject to founder effect and genetic drift Founder Effect - Results in populations that differ from original populations through “sampling error” - Decreases genetic diversity - Occurs by chance - Occurs over and over again in human history because human history is characterized by migration - By chance, so fi a gene is present in the migratory population, it will be in the genetic pool - If a gene is absent, ti will not be in the migratory population - Example: Native Americans have higher occurrence of type O blood *Basically as groups of people separate they bring specific genes with them so one group keeps it and the other loses it* Ellis-Van Creveld Syndrome (genetic disorder that affects bone growth) is common in Amish Communities of Lancaster, PA- a result of Founder Effect Genetic Drift (AKA Wright Affect)- changes in the frequencies of genetic traits over time in a population - Various random processes that affect gene frequencies in small relatively isolated populations - Founders Effect is a kind of Genetic Drift Clines- Because reproductive isolation between populations is never complete, there is some gene flow between populations. The result is clines. - Transition zones between populations - Example: Blood type B in Europe- it gradually decreases in frequency from Eastern to Western Europe *All the human variation that we see today has evolved through genetic drift/founder effect and natural selection* However, the physical environment can produce variation even in the absence of genetic change. Some human variation is due to environmental variation – called Acclimatization (i.e. tanning, shivering) Genotype: The genetic makeup (can’t be changed) Phenotype: The observable physical appearance. (ex: dying hair, contacts etc.) Example of phenotypic variation that is adaptively significant and is subject to natural selection: -Body shape and build -Skin color -Lactose tolerance -Sickle-cell trait and resistance to malaria (all of those traits are differently distributed across the globe because environmental differences resulted in natural selection of one polymorphism over another) Body Build: (i.e. size, shape, relative proportions of limbs to trunk, etc. ) caries in different parts of the globe -Bergmann’s rule: Slenderer populations inhabit warmer parts and robust populations inhabit cooler areas. (Bigger people will not get cold as quickly) -Allen’s rule: Limbs are shorter in cooler environments (to keep in body heat) than in warmer environments (Example: Inuit (artic people) have larger bodies and shorter legs) - Shorter limbs and a more “globular” build decreases surface area in relation to body volume, thus retaining internal heat more efficiently. - In contrast, a long linear build increases surface area to volume, allowing for the dissipation of internal body heat in hot climates. -Gloger’s rule: populations living in warmer climates have more melanin and therefore, darker skin than populations living in colder area with less sunlight Variation in skin pigmentation is an adaptation resulting