There is a reason we have four limbs rather than six like a centaur
(head, arms and torso of a man attached to the body of a horse).
There is a reason we compare our genes with those of numerous other
animals, and why developing the yearly flu vaccine can be tricky.
Explanations for these phenomena and other interesting facts were
revealed in the Evolution in Medicine four-part lecture series
held on campus recently. NIGMS and the Office of Science Education
hosted the series, which was open to employees and the public.
Series planners say evolution is a timely subject for review. "Evolution
unites the disciplines and is foundational to the research we do
at NIH," said Dr. Irene Eckstrand, series coordinator and health
scientist administrator at NIGMS.
Evolution and Development
Dr. Rudolf Raff is a professor at Indiana University and director
of the Indiana Molecular Biology Institute. He is recog-nized as
a pioneer in the field that merges evolutionary and developmental
biology called "evo-devo," described in his book, The Shape of
Life: Genes, Development, and the Evolution of Animal Form.
Raff wants people to "understand that evolution is the underlying
principal that organizes biology. Humans, their food and their pathogens
are all products of evolution," he said.
|Dr. Rudolf Raff discussed some of the misconceptions
society has about evolution and highlighted research findings
in evolutionary developmental (evo-devo) biology.
Evo-devo scientists study body plans (actual body architecture)
in plants and animals over developmental and geological time spans.
Raff's research involves a pair of related Australian sea urchins
(diverged 4 million years ago) that have similar body plans as
adults but follow markedly different pathways to maturity. His
data show that rapid morphological changes are linked to underlying
genetic mechanisms such as the timing and regulation of expression
of specific genes during early development.
Phylogenetic information — graphical representations of
evolutionary relationships between organisms — is vital to
evo-devo, said Raff. With it, you can learn about common ancestors,
evolutionary trends in many biological processes and can make comparisons
between divergent and related species. "In evolution, history matters.
We have four limbs because our fish ancestors developed that way," he
Raff described some common misconceptions about evolution. Claims
that there are no intermediates between major body plans in the
fossil record are incorrect, he said. He cited some well-documented
transitions such as those from fish to amphibian, dinosaur to bird
and ape to human. We've all seen evolution presented as the sequential
morphing of ape to human over time. Raff says this can be "effective,
but misleading." He stressed that in reality, "evolution happens
one generation at a time, during development."
Evolution and Education
Dr. Brian Alters is an international leader in education and the
author of the best-selling book Defending Evolution in the
Classroom. He holds dual appointments with McGill University
in Montreal and Harvard University. He is also founder and director
of the Evolution Education Research Center at McGill.
"Overall, the nation has a big problem," said Alters. "Approximately
half of the U.S. population thinks evolution does (or did) not
occur. While 99.9 percent of scientists accept evolution, 40 to
50 percent of college students do not accept evolution and believe
it to be 'just' a theory," he reported.
Many university students have misconceptions about evolution that
are amazingly ubiquitous, noted Alters. They believe that evolution
is not pertinent to medical research or practice and has no relevance
to AIDS, for example, or to antibiotic resistance in microbes.
Part of the problem is in effective teaching, he said. An instructional
technique known as constructivism works best in the classroom,
he suggested. Essential elements of constructivism include asking
questions that require students to act based on what they think
is accurate and presenting challenges so that misconceptions can
be exposed and alternatives explored.
In the classroom, there is a tendency to separate science and
religion as unique categories without overlap, Alters added. The
separation results in an evolution-versus-creationism (or evolution-versus-intelligent
design) struggle that is being waged in courtrooms and classrooms
across the nation. "The key issue revolves around misunderstanding
the nature of science, particularly that modern science does not
entertain supernatural causation. Modern creationism involves the
belief that a supernatural power intervened in the natural processes
of the development of life on Earth. Proponents want this taught
in science classrooms as science and oppose parts or all of biological
evolution," he said.
Evolution and Genomics
Dr. Eric Green is scientific director of NHGRI and a distinguished
scientist in the field of genomics. Genetics and genomics provide "a
wealth of examples of how evolutionary principles can be used to
gain a better fundamental understanding of basic biological processes
and an understanding of the molecular underpinnings of human health
and disease," he said.
"The Human Genome Project's name may be a misnomer," Green noted.
From the outset, the project intended to make evolutionary compari-sons
of other genomes, including those of the yeast, a fly, a worm and
a mouse. The other species were chosen, in part, because "they
were at distinct evolutionary time points, separated from humans
roughly 80 million to 1,000 million years ago," he said. Evolutionary
comparisons are illuminating details about the human genome and
Evolutionary comparisons also aid in the study of genetic diseases.
For many human diseases, there is a counterpart in animals. In
some cases, the gene mutations responsible for a disease are identical
and may occur in the same gene, Green explained.
"Our ability to interpret the human genome sequence is remarkably
underdeveloped at this time," he admitted. Toward that end, an
important goal is to identify all the sequence elements in the
genome of functional importance, he said. They include sequences
known to code for proteins as well as non-coding regions, sequences
that do not code for proteins but still have a functional role.
Establishing a catalog of functional sequences in the human genome
will help efforts to identify the genetic changes that lead to
complex genetic ailments such as diabetes and cardiovascular disease.
Green credited the work of Charles Darwin, described in The
Origin of the Species, as laying the foundation for one
of the most powerful tools available for interpreting the human
genome sequence. Darwin wrote that it's not the strongest or
most intelligent that survives, but "the one that is the most
adaptable to change." Evolutionary changes that allow a species
to adapt and survive now help scientists identify functional
sequences in the genome. Nonfunctional sequences tend to undergo
change more readily than functional areas, said Green.
Evolution and Infectious Diseases
Dr. Robin Bush is a professor of evolutionary biology at the University
of California at Irvine. She collaborates with scientists at the
Centers for Disease Control and Prevention using computational
techniques and phylogenetic methods to study the evolution of influenza
Bush said the simplest type of phylogenetic tree has three taxa (divergent
groups) that evolved from a common ancestor. "Think of it as a parent
with three children," she explained. The length of the branches indicates
genetic distance or the number of nucleotide changes that have occurred.
A phylogenetic tree of the Orthomyxoviridae family of influenza viruses
shows that strains A, B and C have all come from a common ancestor.
All three infect humans. Strain A also infects pigs, horses and birds.
|Dr. Robin Bush, a professor of evolutionary
biology at the University of California at Irvine, collaborates
with scientists at the Centers for Disease Control and Prevention
using computational techniques and phylogenetic methods to
study the evolution of influenza viruses.
Her research focuses on the genes that code for surface proteins
of the viral coat and how they evolve in response to the host's
immune system. Hemagglutinin (HA) is needed for host receptor binding
and host cell membrane fusion. Neuraminidase is needed for viral
release from the host cell. There are a number of genetic variants
for each of these proteins (H and N lead to such designations as
H5N1). In humans, these proteins are constantly under attack by
the immune system; in response, they have evolved very rapidly
within humans, said Bush.
Bush uses phylogenetic trees to study changes in HA and to look
for patterns between strains. She hopes to predict which strains
may be responsible for the next year's flu and design more effective
and better-targeted vaccines.
Videocasts of the lecture series can be found at http://videocast.nih.gov/ and