Example evolution of cow:

The idea is to have real models of the evolution of the creature that people can touch, sit on etc. They may have little signs next to them like they have in botanic gardens.

 

Graphic Panels
 
 

EXAMPLE: The evolution of corn
 
 

Approximately five major regions of the genome are responsible for the
transition from a teosinte-like ancestor to modern corn.

Two of these regions have been identified recently by John Doebley et al.
(1995).

One maps to a gene (teosinte branched 1) that affects whether a flower
becomes male (tassel) or female (corn cob) and affects the length of side
branches.

A second region also affects length of side branches.

By making appropriate crosses between maize and teosinte, the authors
were able to place alleles within these regions from maize into a teosinte
genetic background.

For every trait that the regions affected, the alleles were less dominant in
teosinte than they were in maize.

"This change in gene action could have resulted from selection during the
domestication process for modifier loci that enhanced the expression of the
trait in the heterozygote."

                                - Doebley et al. (1995)
NEW EVIDENCE FOR CORN'S ANCESTRY COULD LEAD TO INSECT AND DROUGHT RESISTANT
    CROPS

    DURHAM, N.C. -- Scientists continue to debate the ancestry of domesticated
    corn. But Duke University researcher Mary Eubanks said she has mounting
    evidence that corn emerged from the interbreeding of two different wild
    American grasses. Those grasses are Tripsacum dactyloides, also known as
    Eastern gamagrass, and Zea diploperennis, a perennial variety of teosinte.
    By successfully crossing them for the first time, Eubanks has produced
    fertile offspring that closely resemble the earliest known samples of
    primitive domesticated corn, she said in a recent interview. Patented lines
    of her crosses are fertile over several generations and carry genetic
    traits that are "missing links" in corn's evolution, Eubanks adds in the
    latest issue of the journal Theoretical and Applied Genetics. That article
    updates experiments originally described in the June, 1995 issue of
    Economic Botany. She will report on her work again at an August meeting of
    the American Institute of Biological Sciences in Montreal. If Tripsacum is
    indeed a corn ancestor, then breeders could take advantage of some of the
    special traits of that hardy ubiquitous plant, the Duke botany research
    scientist said. Indeed, Eubanks has crossed her lines with modern corn to
    produce hybrids that share Tripsacum's resistance to the corn rootworm.
    That's the root-eating juvenile -- or larval -- stage of an insect that
    costs corn farmers $1 billion a year in crop losses and pesticide
    expenses. In preliminary experiments at Duke's Phytotron, a high-tech
    greenhouse where she rents space, Eubanks found far less root damage and
    far fewer larvae in her experimental hybrids than occurs in normal
    commercial corn. "We're using the western corn rootworm, which is the most
    serious pest in the Midwest," she said. "It's an incredible problem and a
    big expense for corn growers. Because they don't know where they are going
    to have an outbreak, they now have to treat all their fields with extremely
    toxic chemicals." Tripsacum is drought resistant too, and Eubanks plans to
    test her experimental hybrid for that trait as well. Moreover, her
    Tripsacum-teosinte hybrids are perennials, and could conceivably be
    exploited to produce a perennial variety of corn, she added. All of today's
    commercial corn lines are annuals, meaning that their seeds must be planted
    anew each year. Eubanks holds four patents on various Tripsacum-teosinte
    crosses developed during the past decade. She is also president of Sun
    Dance Genetics, a Durham, N.C. research company. Corn is "an anomaly in the
    botanical kingdom," Eubanks said. "You have this tremendous ear. The ear
    has hundreds of kernels, held together on a rigid stalk and enclosed by a
    husk so they're easy to harvest and dry and store. It provided a wonderful
    food for the original inhabitants of the Americas once they began
    cultivating it." But the earliest known versions of corn have far smaller
    ears that bear fewer and tinier kernels, providing silent testimony to the
    corn genome's great adaptability. Scientists are in agreement on the
    ancestry of the Old World's simpler staple grains -- oats, rye and wheat.
    But the origins of the New World's major grain remain cloaked with mystery.
    That's true even though "this is one of the most well studied organisms."
    she said. With a Ph.D. in anthropology, Eubanks would seem an unlikely
    person to pursue research into the molecular biology of corn genes. But,
    while still in graduate school at the University of North Carolina, she met
    Paul Mangelsdorf, a premier corn researcher who had retired from Harvard to
    surrounding Chapel Hill. As an anthropologist, Eubanks was already
    investigating the corn images that pre-Columbian Central Americans
    frequently incorporated in their pottery. And she said that interested
    Mangelsdorf because native American pottery makers pressed real ears of
    corn into the wet clay to form botanically accurate molds. That meant her
    pottery studies could give him vital clues about how domesticated corn
    looked many centuries before the Spanish conquest. So her research trips to
    Mexico and Peru aided Mangelsdorf's continuing work. In turn, Mangelsdorf's
    passion quickly rubbed off on her. Eubanks began studying biology and
    performing botanical research at Duke, Indiana, North Carolina State and
    Vanderbilt universities. Scientists, including herself, now agree that
    teosinte is an ancestor of corn, Eubanks said. Native to Mexico and
    Guatemala, it features corn-like leaves and a tall stalk crowned by
    corn-like tassels. It also has hard seeds that line up
    in a single row -- called a "spike." However, Mangelsdorf once believed one
    of corn's true ancestors was Tripsacum, a grass that ranges throughout
    North and South America. "It's a pervasive weed around here," Eubanks said.
    "It's on roadsides, railroad tracks and
    bridges." The Tripsacum plant resembles corn less than teosinte does. But
    both grasses grow single rows of grain on spikes. And both feature separate
    male and female flowers on the same plant -- just like corn. Moreover,
    Tripsacum occasionally produces paired kernels, a distinctive feature of
    corn linked to the evolution of corn's multiple rows. In contrast to
    teosinte, Tripsacum's kernels are also easy to remove from their hard
    fruitcases, making them accessible as a wild food. And "they are highly
    nutritious and delicious," Eubanks said. Based on breeding experiments in
    the 1930s, Mangelsdorf and other researchers postulated that the earliest
    true corn was derived from a cross between Tripsacum and a now-extinct wild
    corn. Under that view, annually growing teosinte -- the only kind then
    known -- was a later offspring rather than an ancestor. Archeological
    evidence in Central America backed up Tripsacum's role, Eubanks said. In
    the 1960s, Mangelsdorf and colleagues found the most ancient known
    preserved corn samples, believed to be more than 5,000 years old, within
    dry caves in Mexico's Valley of Tehuac‡n. The earliest samples of teosinte
    have been dated to 1800 B.C. And the
    earliest evidence for Tripsacum, found at Tamaulipas Mexico, predates that
    teosinte by about 500 years. Nevertheless, Mangelsdorf joined the teosinte
    bandwagon in the 1980s after other researchers discovered Zea diploperennis
    growing on the threshold of extinction in the mountains of Jalisco, Mexico.
    Rescued from the wilds, lines of that perennial teosinte are now being
    maintained for research purposes. Mangelsdorf's new hypothesis, which he
    held until his death, said annual teosinte resulted from a cross between
    perennial Zea diploperennis and an extinct line of early corn. Domesticated
    corn then arose from crosses between that corn and the new annual
    teosintes. Most other experts believe natural genetic mutations actually
    caused the spikes of some wild teosinte plants to directly evolve into the
    first primitive ears of corn, Eubanks said. Under that hypothesis, Native
    Americans then improved the first corns through accidental or intentional
    breeding efforts. But Eubanks maintains that Tripsacum is corn's other
    ancestor plant. And the discovery of perennial teosinte is helping her
    prove that hypothesis, she said. Her initial breeding experiments showed
    that -- unlike any other teosinte -- Zea diploperennis can be successfully
    crossed with Tripsacum to produce a fertile hybrid. Previous attempts to
    breed Tripsacum with any other teosinte varieties had failed. Similarly,
    previous attempts by breeders to cross Tripsacum with corn always resulted
    in sterile plants. But Eubanks found she could also successfully breed corn
    with some of her Tripsacum and Zea diploperennis crosses. Since fertile
    offspring implies genetic similarities among plants, Eubanks believed her
    experiments rekindled the notion that Tripsacum was a forebear of corn.
    Other scientists initially didn't accept her hypothesis. "It questioned
    accepted dogma," she said. "I had difficulty convincing the scientific
    community that I even had a hybrid between Tripsacum and the perennial
    teosinte. They said I just had teosinte that was contaminated with corn,
    and that it was impossible to cross teosinte with Tripsacum." Eubanks said
    she continued in the face of criticism because she knew her work had
    already been validated by the U.S.
    Patent Office's rigorous documentation process. She also persisted because
    of her plants' potential contributions to agriculture and human welfare,
    she added. Seeking further proof, Eubanks used molecular genetic analysis
    to show that traits from both plant types were present in the offspring.
    She worked with key heritable DNA markers that other scientists --
    including her principal detractor -- had previously identified as being
    crucial in the evolution of domestic corn. Her new report in Theoretical
    and Applied Genetics shows some of those markers have now been "stably
    inherited" for three generations, she said. Eubanks is now embarked in an
    expanded study of the complex genetic relationships between teosinte,
    Tripsacum, primitive corns and other related New World grasses. The
    National Science Foundation's Small Business Innovation in Research program
    is funding Eubanks' research on corn rootworm resistance. She is conducting
    her evolutionary studies of corn and related grasses under an Andrew P.
    Mellon fellowship in plant systemics at Duke. She has also supported her
    work from earnings as a self-employed consultant, and by teaching advanced
    high school biology at the North Carolina School of Science and Mathematics
    and Durham Academy. With funding from the National Geographic Society, she
    is now completing a book about the interdisciplinary archaeobotanical
    studies she did in the 1970s of corn impressions on Mexican and Peruvian
    pottery. The book, called Corn in Clay, will be published by the University
    of Florida Press. "There are two Peruvian pieces in the collection here at
    the Duke Art Museum," she noted. "There is one that depicts a rat eating an
    ear of corn. Then there is one that represents a basket of corn." The first
    piece is "somewhat problematic," Eubanks said. The corn casts it carries
    have more rows and larger kernels than any Latin American race of corn that
    exists today. "We think it may represent an extinct race," she added.

    http://www.dukenews.duke.edu/research/corn.html
    June 4, 1997 Contact: Monte Basgall (919) 681-8057 [email protected]
 

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