Evolving A.D.: After Darwin, Science Exploded
Listen to an interview with blackberry breeder John Clark on KUAF 91.3 FM.
In the 150 years since Charles Darwin’s landmark book, the knowledge that species evolved through natural selection has opened the door to tremendous advances in science. University of Arkansas professors discuss evolution in a variety of fields.
Professor of anthropology, J. William Fulbright College of Arts and Sciences.
Darwin profoundly changed our view of ourselves,” said anthropologist Michael Plavcan. “Evolutionary biology makes us part of the world rather than the center of the world.” At the same time, the study of humans raises particular questions, such as “how culture should be factored into understanding the evolution of human intelligence.
“As humans became more dominant, we became more effective at exploiting the environment,” Plavcan said. When we don’t have to worry about predators, and when we are able to insure that food will be available throughout the year, “what becomes important is the ability to navigate social systems.”
“For animals, the ability to run fast and not get eaten is primary over the ability to make friends,” Plavcan explained. “But humans have occupied a niche that has reduced other pressures, allowing sociality to become dominant. To survive, I must be able to know that you will think as I do and react the way I expect. Humans have become good at thinking about what other humans think and assigning cause and effect.”
Plavcan’s research centers on primate and human evolution. He uses comparative analyses of living species to understand the morphology and adaptations of extinct species. Applied to the fossil record, his work has been used as a basis for inferring the evolution of social behavior in primates and early humans. In 2009, his colleagues recognized the significance of his work by naming him a Fellow of the American Association for the Advancement of Science.
David A. Schroeder
Professor of psychology, J. William Fulbright College of Arts and Sciences.
David A. Schroeder studies pro-social behavior, a field that increasingly includes examining the genetic basis for human behavior.
“One way to insure our genes survive is to insure survival of our offspring,” Schroeder said. “Thus, doing good things for close family relations has beneficial consequences.”
The phrase “blood is thicker than water” acknowledges the pull of kinship in helping others. Humans recognize their own offspring quickly, and Schroeder said, “Research has shown a correlation between degree of relatedness and likelihood of helping others.”
There also appears to be an evolutionary root to empathy, Schroeder said. “We may be genetically predisposed to vicariously experience emotion and feel the pain of others. For example, within one day of birth, babies exhibit a sense of empathetic connection with other babies who are crying to express distress.”
Another basis for helping is reciprocal altruism, the social norm that if I do something nice for you, you will do something nice for me. There appears to be a genetic drive for such reciprocity.
“Recent evidence suggests that individuals not only reciprocate, but some are inclined to punish those who do not reciprocate, even at some cost to themselves,” Schroeder said. “There appears to be an evolutionary basis for punishment in social order, for bringing people back in line who do not reciprocate.”
Research has shown that, over time, groups with more cooperators do better than those with more competitors. In many cases, Schroeder observed, “Cooperation proves to be superior to competition in the long run, although competition may do better in the short run. The rule is “survival of the fittest” and sometimes being cooperative and pro-social is what being fit really means.”
John R. Clark
Professor of horticulture, Dale Bumpers College of Agricultural, Food and Life Sciences and the Division of Agriculture.
Horticulturalist John R. Clark directs the world’s largest blackberry breeding program, as well as breeding projects for a wide variety of fruits and nuts. He and other plant breeders call their work “controlled evolution.”
“In our plant breeding, genes come together by design, rather than by birds, insects, wind or other forms of natural gene transfer,” Clark said. “Agriculturists also adjust the environment through practices such as irrigation and control of competing weeds.”
For hardy, disease-resistant genes, breeders look for “centers of origin” as sources of genes that exist in the wild, such as blackberries in eastern North America. James N. Moore, a Distinguished Professor Emeritus who founded the blackberry-breeding program 45 years ago, crossed early hybrids developed from native U.S. blackberries with other sources, including English thornless hybrids. Subsequent selection resulted in plants with improved berry size and taste, often with thornless canes.
In a process based on the 19th century work of Gregor Mendel, breeders cross-pollinate blackberry plants, collect seeds, grow seedling plants and continue the process until they find the one plant with the desired traits. From first crossing to variety release can take a decade or longer.
Most breeding is done at the Division of Agriculture’s Fruit Research Station in Clarksville, AR, but Clark also oversees testing and breeding of blackberries in Europe, Central and South Africa, Japan and Australia. By learning how genes perform in different environments, blackberry breeders make it possible for growers worldwide to offer nutritious fruit to local markets. This work may also help producers adjust to global climate change and insure a stable food supply.
“We need to be aware of changes in the environment and match genetic resources that are adapted for that environment,” Clark said. “We’ve created a genetic resource here. We have to ask: Is there a way to maximize its useful evolution and to enhance quality of life?”
Professor of biological sciences, J. William Fulbright College of Arts and Sciences.
Biology professor Cindy Sagers has spent much of her career studying a special relationship between ants and tropical plants that seemingly shouldn’t exist. In some cases, ants and plants cooperate to form a mutual system where the ants take some of their nutrients from the plants, but also “feed” the plants in return.
“The evolution of this kind of cooperation has been a longstanding puzzle in evolutionary biology,” Sagers said. For this kind of relationship, the plants and ants must have co-evolved.
To get to the roots of this puzzle, Sagers and colleagues plan to study ant-plant interactions in different ecosystems throughout Mexico, Central America and South America. They will study the insects and plants to determine their relationships, run genetic studies to determine the species involved and examine the ecosystems where the particular pairings are found to look for co-evolutionary “hot” and “cold” spots.
“If we can understand the ecological factors that contribute to the variation, we can get to the ecological factors that contribute to co-evolution,” Sagers said. “We cannot understand the relationship between these ants and plants in isolation.”
William J. Etges
Professor of biological sciences, J. William Fulbright College of Arts and Sciences.
Fruit flies have become the “lab rats” of the insect world. They can be found pretty much anywhere there is decaying plant matter. Further, because fruit flies have diversified into thousands of species, reproduce quickly and create many generations in a short time, scientists can use them to study evolution, population genetics and species formation.
Biology professor William J. Etges studies cactophilic Drosophila, fruit flies that live in deserts and feed on decaying cacti. While many fruit fly researchers work solely in the laboratory, Etges goes to the desert to study these species in their environment.
Species formation is considered to be a matter of reproductive isolation over time — in other words, two populations become so different that they do not mate or produce viable offspring. Most fruit flies live in mild climates, but a number of species such as D. mojavensis have colonized the desert, using fermenting cactus and surviving in high heat and low water conditions. Etges and his colleagues are identifying genes that have helped the fruit flies adapt to these harsh conditions.
“Eventually we want to know about the larger-scale patterns that explain how species are formed,” Etges said.
Professor of biological and agricultural engineering, College of Engineering and Dale Bumpers College of Agricultural, Food and Life Sciences.
Evolution at its most basic level involves changes in genes, and nowhere is this more apparent than in viruses. Scientists argue about whether or not these tiny strands of RNA constitute living species, but there is little doubt that they evolve. And they evolve extremely rapidly -that’s why everyone needs a new flu vaccine every year.
This poses a challenge for biological engineer Yanbin Li, who has worked with a team of scientists to create a biosensor that can rapidly detect the avian flu virus in the field.
“The avian flu virus can change in several days to several weeks,” Li said. Eventually, enough mutation could make it difficult to detect the avian flu by standard methods.
Current research is looking for ways to determine which areas of viral RNA change rapidly, which could help scientists determine how best to ensure that mutations don’t make it difficult to rapidly detect avian flu.
“Now we can see how they mutate and how under some conditions they are going to mutate,” Li said. This will help create better biosensors so that deadly viruses can be detected before birds — or people — have symptoms, thus lowering the risk of an epidemic.
Associate professor of crop, soil and environmental sciences, Dale Bumpers College of Agricultural, Food and Life Sciences.
In the war against infection, humans use antibiotics to vanquish bacteria. And bacteria fight back through evolution – the bacteria that survive the onslaught of antibiotics reproduce and strengthen antibiotic resistance in the remaining bacterial population.
While others ponder the effects of this problem on the human body, professor Mary Savin is examining the effects of antibiotic resistance on stream ecosystems that regularly receive treated effluent from waste management facilities.
She has examined creeks near such facilities and found low levels of antibiotics in the water downstream from the plants.
“The antibiotics are found at low levels, but they are there,” she said. “We want to know if these low levels are enough to change resistance levels in bacterial populations.”
To do so, the researchers are looking at E. coli found upstream and downstream of the point where effluent enters the stream. They are examining the bacterial isolates to check for genes that confer antibiotic resistance, but they also are looking at total bacterial diversity of resistant isolates as well as any changes in diversity from upstream to downstream. They also are looking to see if the antibiotic resistance is something that disappears with time and distance from the effluent source.
“It’s possible that the effluent is contributing to antibiotic resistance,” Savin said. “Whether it will change its effect on the ecological community is another matter.”
Assistant professor, biological sciences, J. William Fulbright College of Arts and Sciences.
Biologist Jeff Silberman spends his time studying the origins and relationships among the “oddballs” of the Tree of Life – single-celled eukaryotes, or organisms that have a nucleus, such as anaerobic organisms, amoebae and flagellates, some of which are parasites. He performs comparative DNA sequence analyses of these extremely basic organisms to help find their particular branch on the Tree of Life.
These “oddballs” and humans have more in common than most people realize — animals, plants, protists and fungi are all eukaryotes, that is, all of these creatures have cells with complex organelles, such as a nucleus and mitochondria. Mitochondria in aerobic organisms power cells by using oxygen to produce energy. They also are involved in the regulation of cell growth and cell death. Mitochondria in anaerobes differ from those in aerobic organisms, and energy production does not seem to be their main function.
“There are lots of things we don’t know about the basic functions of cells and their organelles,” Silberman said.
Being anaerobic doesn’t seem to be a primitive trait. Anaerobic organisms can be found throughout the eukaryotic tree, indicating that it is a an adaptation that has evolved many times independently.
By isolating formerly unexamined anaerobic protists and looking at the independent ways they have formed different types of mitochondria, Silberman hopes to reveal essential commonalities among all eukaryotes, perhaps even clues to the origins of eukaryotes.