Lecture Summaries

Thursday, December 1, 2005

Lecture One

Endless Forms Most Beautiful
Sean B. Carroll, Ph.D.

Webcast 10:00 a.m.-11:00 a.m. ET

The Darwinian revolution was the first revolution in biology. This lecture traces the discovery of evolution through Charles Darwin's long voyage, many discoveries, and prodigious writings. It is a dramatic story of how a medical school dropout and future clergyman transformed our picture of nature and our place in it. Darwin developed two great ideas in The Origin of Species that have shaped 150 years of evolutionary biology: the descent of species from common ancestors and their modification through natural selection. Darwin also introduced the concept of the "fittest," but how are the fittest made?

The second revolution in biology was triggered by discoveries in genetics. Genetic variation, selection, and time combine to fuel the evolutionary process. The action of selection is now visible in DNA, both in preventing injurious changes and in favoring advantageous changes in traits.

Break
11:00 a.m.–11:30 a.m. ET

Lecture Two

Selection in Action
David M. Kingsley, Ph.D.

Webcast 11:30 a.m.-12:30 p.m. ET

The products of natural, and human, selection are all around us. Humans have transformed wild plants into useful crops by selective breeding. Human selection has also produced pets and other domesticated animals with sizes and shapes very different from their wild ancestors. Controlled genetic crosses can be used to identify and locate the genes responsible for artificial selection in domesticated species. Genetic crosses in maize and dogs, for example, suggest that relatively few genetic changes are needed to dramatically transform the shape and structure of plants and animals.

Natural selection in wild populations can also generate amazing diversity in a surprisingly short amount of time. Ocean stickleback fish, for example, colonized numerous freshwater streams and lakes produced by retreating glaciers after the last ice age. Differential survival and reproduction under natural selection have generated dramatic changes in morphology, physiology, and behavior as the fish adapted to different food sources, predators, and water conditions. How does nature convert a marine ancestor into diverse freshwater forms? Once again, genetic studies suggest that major evolutionary changes are controlled by a few key genes. Further study of such genes will provide a molecular portrait of how plants and animals have been transformed by artificial and natural selection.

Friday, December 2, 2005

Lecture Three

Fossils, Genes, and Embryos
David M. Kingsley, Ph.D.

Webcast 10:00 a.m.-11:00 a.m. ET

Recent studies have identified important genes that direct embryonic development. Specific developmental regulators control the formation of particular tissues or help define larger body regions, such as heads and tails, backs and bellies, forelimbs and hindlimbs, or the left and right sides of the body.

Many key developmental genes are conserved among animals that look very different. A diversity of body forms can emerge from changing where and when these shared developmental regulators are expressed. For example, fins and limbs have been extensively modified in many different animals. Major changes in the fins of stickleback fish occur by altering the expression pattern of a major developmental control gene involved in hindlimb development. Intriguingly, fish evolving independently in widely separated waters have alterations in the same basic genetic and developmental elements. Fossils suggest that similar developmental mechanisms were used in animals that evolved millions of years ago.

The great extent of shared developmental machinery reveals a deep common ancestry for living forms and makes it possible to discover general rules of evolution from highly detailed studies of diverse organisms.

Break
11:00 a.m.–11:30 a.m. ET

Lecture Four

From Butterflies to Humans
Sean B. Carroll, Ph.D.

Webcast 11:30 a.m.-12:30 p.m. ET

The story of animal evolution is marked by key innovations such as limbs for walking on land, wings for flight, and color patterns for advertising or concealment. How do new traits arise? How has the great diversity of butterflies, fish, mammals, and other animals evolved? The invention of insect wings and the evolution of their color patterns are beautiful models of the origin of novelty and the evolution of diversity. This lecture explores how new patterns evolve when "old" genes learn new tricks.

Old genes learning new tricks also applies to our own species and the evolution of traits that distinguish us from earlier hominids and other apes: our big brain, bipedal locomotion, and speech and language. The complete picture of human evolution involves new information emerging from the fossil record, genetics, comparative physiology, and developmental biology. Despite immense advances in evidence and understanding, there remains a societal struggle with the acceptance of our biological history and the evolutionary process, the roots of which are discussed in this lecture.

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