By Michael Alan Park, Ph.D. Central Connecticut State University McGraw-Hill

Themes of Anthropology: Evolution Chapter 3 Themes of Anthropology: Evolution

As You Read, Consider: What effect did the Bible have in the development of evolutionary thought? What major scientific disciplines contributed evidence in support of evolutionary theory? In what ways did Darwin’s theory fall short in explaining evolution? What are the basic concepts of modern genetics and inheritance, and how do these contribute to our understanding of evolution? What is adaptation? In what way is adaptation at the heart of evolutionary theory? What is the evidence for biological evolution? What are the major forces of evolution? How do new species evolve from existing ones?

The Evolution of Evolution Since the time of the ancient Greek philosophers, the idea has persisted that biological species, including humans, have changed over time and have given rise to other species.

Definitions Natural Selection: Evolutionary change based on the differential reproductive success of individuals within a species. Inheritance of Acquired Characteristics: The incorrect idea that traits acquired during an organism’s lifetime can be passed on to its offspring. Evolution: In biology, the idea that species change over time and have a common ancestry. Fossils: Remains of life-forms of the past.

Some Basic Genetics At about the time Darwin was writing Origin of Species, an Austrian Monk named Gregor Mendel, working in a monastery, described the basic laws of inheritance.

Definitions Mutation: Any spontaneous change in the genetic code. Genotypes: The alleles possessed by an organism. Homozygous: Having two of the same allele. Heterozygous: Having two different alleles in a gene pair. Gametes: The cells of reproduction which contain only half the chromosomes of a normal cell.

Definitions Genes: Technically, those portions of the DNA molecule that code for the production of specific proteins. Alleles: Variants of a gene that code for different expressions of a trait. Dominant: The allele that is expressed in a pair of unlike alleles. Recessive: An allele that is only expressed if present in a like pair. Phenotype: The chemical or physical results of the genetic code. Co-dominant: When both alleles of a pair are expressed in the phenotype. Asexually: Reproducing without sex, by fissioning or budding.

Adaptation What processes bring about new species? First, a species looks and behaves the way it does because it is adapted to its environment. Why do species look and behave as they do? Second, different species exist because in the continual process of adaptation, species can and do give rise to new species.

Definitions Adapted: When an organism has physical traits and behaviors that allow it to survive in a particular environment. Descent With Modification: An old term for what we now call biological evolution. Ecology: The science that studies the network of relationships within environmental systems. Niche: The environment of an organism and its adaptive response to that environment. Habitat: The place occupied by a species; the species’ “address.” Ecosystem: A specific set of environmental relationships. A unit of study within ecology.

Descent with Modification If environments always stayed the same, organisms would not have to change their adaptive characteristics and behaviors. All living things today would be essentially like the very first living things. This, of course, is not the case.

Definitions Proteins: Molecules that make cells and carry out cellular functions. Amino Acids: The chief components of proteins. Deoxyribonucleic Acid (DNA): The molecule that carries the genetic code. Ribonucleic Acid (RNA): The molecule that, in two forms, translates and transcribes the genetic code into proteins. Strata: The layers of rock and soil under the surface of the earth. Stratigraphy: The study of the earth’s strata. Artificial Selection: Selection for reproductive success in plants and animals that is directed by humans. Gene Pool: All the genes in a population. Chromosome: Strands of DNA in the nucleus of a cell.

Definitions Gene Flow: The exchange of genes among populations through interbreeding. Genetic Drift: Genetic change based on random changes within a species’ gene pool. Fission: Here, the splitting up of a population to form new populations. Founder Effect: Genetic differences between populations produced by the fact that genetically different individuals established the populations. Gamete Sampling: The genetic change caused when genes are passed to new generations in frequencies unlike those of the parental generation. Speciation: The evolution of a new species.

The Origin of Species Environment and adaptation are responsible for the modification of species as well as the evolution of new species or speciation.

Definitions Macromutation: A mutation with extensive and important phenotypic results.

Questions for Further Thought Is the history of evolutionary thought a battle between science and religion? What is the relationship between these areas of inquiry in the history of evolution? Given that all life is related in a giant “family tree,” how might this fact influence ethical considerations, especially with regard to our relationships with other species? Do we give greater consideration to species closely related to us? How close is “close”? What are the criteria involved: shared biological characteristics, the same branch of the family tree?