Stories tagged History and Nature of Science

Jan
12
2006

The University of Witwatersrand in Johannesburg South Africa has long been known for its impressive discoveries related to human evolution. Discoveries from Witwatersrand related to human evolution typically emphasized the importance of not only Africa but South Africa in the development of early man. Many of the more famous discoveries related to Paleoanthropology or the study of human evolution come from East Africa — where researchers have discovered, and continue to discover, some of the best evidence for human origins in Africa. Researchers further south, however, continued to argue that fossil discoveries from South Africa should not be discounted from the developing picture of the history of early man.


Raymond Dart with Taung skull: Raymond Dart with Taung skull Credit

One of the most significant South African discoveries was the Taung child, which was discovered in 1924 and was given its name when the first researchers to examine the fossil concluded that the specimen was so small because it was a child. This week, researchers from Witwatersrand are announcing that the Taung child could have been killed by a large bird. Yahoo News is reporting that by studying the hunting abilities of modern eagles in West Africa, researchers determined what signs would be left behind on a skull of an animal that was killed by a predatory bird. Armed with this new knowledge, Physical Anthropologists reexamined the Taung child and found traces of cuts behind the eye sockets. Even though the specimen has surely been examined hundreds of times since its discovery, nobody had really noticed the marks before.

Discoveries like this one prove that new discoveries and interpretations can be made by simply reexamining old discoveries with a fresh pair of eyes. No pun intended.

Dec
29
2005

The journal Science has named a few studies that followed evolution in action--in influenza viruses, chimpanzees, and stickleback fish--"Breakthroughs of the Year."

Science Blog explains the significance of these studies, and the rest of the "top ten" science achivements of the year.

Dec
08
2005

Ever notice that uncooked spaghetti doesn't break neatly in two when you bend it? Instead, it shatters into several pieces of different lengths. Why?

Researchers recently solved the spaghetti mystery and improved scientists' understanding of how things shatter. Because strands of spaghetti are similar in some ways to lots of brittle objects—from industrial cutting tools to body armor—knowing why spaghetti breaks the way it does may help make those things stronger and safer.

Spaghetti catapult
The researchers clamped one end of a piece of spaghetti in place, and then bent the rod until it was just about to break. Then they let the unclamped end go, and filmed the results with a digital camera that took 1,000 images per second. The pictures showed that the spaghetti rod didn't spring back to its original position like a diving board would. Instead, the release caused ripples that ran down the rod's length and bounced back from the clamped end. The spaghetti snaps where the curvature is greatest—where the ripples from the free end meet the ripples bouncing back from the clamped end. And it happens again in the remaining piece of spaghetti each time the rod breaks. (See some movies of the breaking spaghetti.)

Just getting started
Now scientists know why spaghetti breaks into more than two pieces, but the new research opens up many more questions about how objects shatter.

MAKE IT at the Museum
The recent spaghetti discovery was made possible by an extremely high-speed camera that captured photos of how the pasta bent and broke. On Saturday, December 10, between 1:30 and 3:30, you can make a zoetrope and watch some spaghetti "filmstrips" for yourself. It's free, it's fun, it only takes a few minutes, and you can take your creation home with you when you're done.

Nov
15
2005


Singing Mouse Photo

Researchers at Washington University in St. Louis have discovered that mice sing.

Scientists already knew that mice make ultrasonic sounds-squeaks that are too high-pitched for us to hear without special equipment. But these scientists used microphones and computer software to study the squeaks of 45 male mice.

What's in a song?

The researchers separated the squeaks into types of syllables based on how quickly the pitch rose or fell. The mice "sang" about 10 syllables per second. And almost all of the mice repeated sequences of syllables in clear patterns. None of the mice are Marvin Gaye, exactly, but their noises meet the scientific definition of song. (People, birds, whales, and some insects do the same thing.)

Why sing?

Researchers still have to figure out WHY the mice sing. Because the mice sang in response to pheremones-chemicals that transmit messages between animals of the same species-one guess is that male mice sing to impress females.

Hear the mice singing.

Oct
18
2005


Whooping cranes and an ultralight: Because of Operation Migration, now in its fifth year, 40 adult birds in the flock now make the migratory flights south in the fall and north in the spring on their own. Photo © Operation Migration


Whooping crane: An adult whooping crane (Photo courtesy USGS)

On Friday, a group of endangered whooping cranes took to the skies, migrating from Necedah, Wisconsin, to their winter habitat in Florida—1,200 miles away.

The 20 cranes, which were hatched and raised in captivity, have to be taught to migrate. (Whooping cranes learned their migration route by following their parents, but the knowledge was lost when the population dwindled and no wild birds used the flyway.) So Operation Migration's pilots in ultralight planes lead the birds south.

The birds' route takes them from the Necedah National Wildlife Refuge, in Wisconsin, to the Chassahowitzka National Wildlife Refuge in Florida. Read the Operation Migration field journal to see where the flock is today and what's been happening to them.

(The Patuxent Wildlife Research Center, which also helps to raise endangered whooping cranes, has links to lots more resources.)

Oct
12
2005

A visitor to this website recently posted this question:

How is evolution proved right? How is there proof of this "chance?" There are many other ways people say the earth was created; which is right? Is there a God that created the world? Or did everyone simply evolve? Whatever you believe, how do you prove yourself right?

Here is the Science Museum of Minnesota's official position on evolution.

That said, "proof" is really the crux of the issue.

All explanations of the Earth's creation other than evolution basically say that life is too complicated to explain by natural processes; something outside of nature must have created it. The only way to prove or disprove an idea like that is to look outside of nature. And once you go outside of nature, you're no longer doing science.

Science is a way of looking at the world, asking questions about nature and looking for answers in the natural processes around us. It works on one simple rule: show us the evidence! Show us an experiment in the lab or an observation in nature, but you have to point to something real that can be seen or measured. And then you have to come up with an explanation for what you've seen. You have to test your explanation by doing another experiment or making another observation that supports you. And if the results don't match, you know your explanation was wrong.

In science, a theory is an explanation that accounts for all the evidence. Atomic theory explains how matter works. Gravitational theory explains how gravity works. And evolutionary theory explains how life has changed over time.

Evolution is both a fact and a theory. The word has two meanings. First, it means "the history of life on Earth." And there's no denying that life has changed over the last 500 million years-go to the Dinosaurs and Fossils Gallery and see for yourself. But evolution also means "the explanation of HOW those changes have occurred." Scientists use the word theory for explanations that account for all the evidence.

And there is a lot of evidence for the theory of evolution. Every fossil that's ever been found; every animal that ever lived; every cell in your body-all of these support evolution. Scientists have been poking and prodding and testing the theory for 150 years, and have written tens of thousands of papers on the subject. Evolution is the best explanation we've ever had for the history of life on earth. (In terms of experiments and observations, it has been said there is more solid evidence for evolutionary theory than for atomic theory-and no one doubts the existence of atoms!)

Evolution happens every day, all around us. The bird flu that's been in the news is an example of evolution in viruses. New breeds of farm plants and animals are examples of evolution. And every baby that is born today will inherit traits from its mother and father, and so also be an example of evolution in action.

Science is really good at explaining WHAT and HOW: what our bodies are made of, how they work, how we evolved. But one thing science cannot do is explain WHY. Why are we here? What is our purpose? What is life's meaning? For that, you need religion.

OK, so what is evolution?
Evolution, by the most basic definition, is the profound, ceaseless change in life forms through time.

Charles Darwin and Alfred Wallace were the first scientists to call this change in life over time "natural selection," although many others have contributed to the idea. (Changes in the theory of evolution have been made since Darwin's original proposal, yet his main theory stands firm.)

The theory of natural selection is based on three principles:

  • Organisms produce more offspring than can survive and reproduce.
  • Those that do survive tend to be better adapted to local environments.
  • Most adaptations are genetic, so they can be passed from parent to offspring.

Generation by generation, organisms that are better adapted to their environment in some way survive to pass on their advantageous qualities.

Evolution is not purposeful: it does not work toward a specific end or create better or worse organisms. Species evolve by adapting to particular niches in their environments, but the genetic mutations that lead to these adaptations occur by chance. An organism cannot will itself to mutate in a beneficial way. If its niche disappears, the species may become extinct or it may adapt to new conditions, but the failure to do so does not imply some kind of defect.

Evolution does not occur "for the good of a species." It operates at the level of individual organisms over many generations. A whole population does not simultaneously evolve a new trait; instead, the new trait evolves in one or a few organisms, which pass it on until the population is dominated by organisms having that trait.

Even more evidence of evolution
As humans, we share features with all living life forms, past and present. The more specific these features are, the more recently scientists think they evolved. For example, fingernails-a feature we share with all primates-evolved 30 million years ago. We have the same basic anatomical plan as all other vertebrates, which evolved 500 million years ago. And our cells'ability to use oxygen goes all the way back to our relationship with plants, fungi, and bacteria, which evolved over 1,000 million years ago.

Here are other examples of evidence for evolution:

  • Some animals have organs that serve no purpose but have a function in other species. Such a structure is referred to as vestigial. Whales, for instance, possess useless pelvic bones left over from their land-dwelling ancestors. Fossil whales are found with tiny limbs that became increasingly unimportant.
  • Many closely related species live in proximity to one another but are separated by a geographical barrier. (It was observations like this on the Galapagos Islands that helped Darwin formulate his theory of natural selection.) For example, two similar species of fish live separated by Central America: one in the Gulf of Mexico, and the other in the Pacific Ocean. They evolved when the Isthmus of Panama formed and separated their common ancestor's population into two groups. If the fish had not evolved after they were separated, the same species would live on both sides of the isthmus. And if they hadn't descended from a common ancestor, they wouldn't be so similar.
  • As we develop more types of antibiotics, new resistant strains of bacteria evolve through natural selection. Many crop pests have also evolved strategies to cope with our use of pesticides. Some species of grass have even evolved ways of thriving on industrial waste.
  • Through artificial selection, humans have developed new plants and animals. By manipulating genes, we have obtained many different types of crop plants-some produce greater yields, some produce higher concentrations of their own natural pesticides, and some are more resistant to drought. From a very basic canine type, we developed many different breeds of dogs over the last few thousand years. Artificial selection is somewhat analogous to natural selection; the difference is in the selective force-humans, instead of nature.
  • All multi-celled creatures share distinct genes for developing body plans (like plans for limbs, eyes, etc.). These genes, called homeotic genes, are incredibly similar in all animals, even among animals as different as fruit flies and chimpanzees.
Sep
20
2005

It's time for the annual wild rice harvest.

The traditional harvesting technique requires one person to pole a canoe and one or two other people to gather grain. They beat the stalks with paddles, sweeping about half the rice into the boat. The rest of the grain falls to the bottom of the lake, where it sprouts the next spring.

But wild rice in Minnesota is threatened in many ways, and many lakes have produced a poor crop.

Wild rice, or Zizania palustris, is actually an aquatic grass. To grow, it needs shallow water and a mucky bottom. Drainage and damming of wetlands or lakes for farming or reservoirs have destroyed wild rice habitat. (Wild rice once grew throughout Minnesota and the eastern United States. In Minnesota alone, there are 70 Rice Lakes and 25 other lakes with "Rice" in their names, even though wild rice may no longer grow there.) And runoff of herbicides and nutrients from farm fields kills rice, too.

Fluctuating water levels are tough on the plants. When wild rice sprouts in the spring, a tiny root anchors the seed in place. When the stalk reaches the surface, long leaves form, floating on the surface of the water. If the water level rises, the weakly rooted stalk is pulled up and the plant dies. If the water level drops, the weak stalk collapses, killing the plant.

Carp often kill wild rice seedlings. They're bottom-feeders, digging up and disturbing young plants as the fish search for food. (These fish are not native.)

But there's another threat: for decades, the University of Minnesota has been researching wild rice, aiding in the development of 25,000 acres of machine-harvested, cultivated paddy rice in Minnesota. See, the seed head of the wild grain shatters easily. That allows the plant to seed itself, but makes it tough to farm commercially. Many fear it's just a matter of time until scientists genetically modify the wild rice genome, and contamination by genetically modified rice might decrease the economic and cultural value of the wild grain.

"We consider the wild rice to be a sacred gift from the Creator and it's always been here for us. Now, if the rice is altered genetically, it may be a strain that will take over the wild rice, and we will lose what was given to us by the Creator."
(Earl Hoagland, Ojibwe tribal elder)

(Not everyone agrees that the genetic research is a problem.)

Bills banning genetically modified wild rice in Minnesota (supported by White Earth Band members) didn't make it through the last legislative session, but will be reintroduced next year.

But here's the good news. At Lower Rice Lake on the White Earth Indian Reservation (north of Detroit Lakes), where lakefront development is prohibited and the White Earth Land Recovery Project manages the watershed, 200 people participate in the traditional harvest, gathering 11,000 to 15,000 pounds of rice a day, or 200,000 to 300,000 pounds each year. The rice is processed locally and sells for about $8.50 a pound. The grain itself feeds many White Earth families, and the proceeds from the rice harvest are a significant chunk of the annual income of many families.

Aug
12
2005

Is that a contradiction in terms?

Approximately 330 million tons of garbage filled landfills in the United States last year alone, according to Solid Waste Digest, a trade publication for the waste industry. However, remarkably, the capacity of these landfills has been increasing even though very few new dumps are being built. How is this possible?

It turns out that landfill managers have been using methods that allow them to pack more trash into a landfill then what was previously thought possible. Some landfills pile tons of dirt on top of sections of their dumps and then six months later scrape the dirt aside. Like stomping your foot into the waste bin to make more room, this system works to create 30 to 40 more feet of depth — more space for more trash.

Other methods to increase landfill capacity include blowing water and air into the dumps to quicken decomposition and therefore reducing the size of buried garbage. Or, they are using other methods, such as giant 59-ton compacting machines, to bury trash more tightly.

The good news here is that this efficiency will help to reduce the need for new landfills. The bad news is, again, the United States produces 330 million tons of garbage a year! New York City produces so much garbage that it exports 25,000 tons of trash every day to other states and other cities.

So, while I think this new efficiency is great, I also think that we (you and I) still play a significant role in reducing the amount of trash put into landfills. Reduce, reuse, recycle!

Jul
28
2005

A part of the energy bill currently up for a vote amends the Uniform Time Act of 1966 to extend standard daylight time from the second Sunday in March to the first Sunday in November. Currently standard daylight time runs from the last Sunday in April to the last Sunday in October. This will reduce daylight savings time (DST) by four weeks beginning in 2007 if the Department of Energy verifies research that shows the cut would save energy.

The main purpose of DST is to make better use of daylight. We change our clocks during the summer months to move an hour of daylight from the morning to the evening. The Department of Energy says the extra daylight in the evening will help America use less electricity for lighting and appliances. Studies done by the U.S. Department of Transportation in the past show that DST does reduce the country's electricity usage by a small amount. Business owners and sporting groups support the plan saying it would increase retail sales and participation in outdoor activities. Canada is closely watching this measure in the energy bill, and will likely change their DST to match the U.S.

Several groups are opposed to the plan. Airlines are concerned that a change of DST in North America would result in international schedules to become further out of sync with Europe and the rest of the world. The National PTA also is against the extension because it will result in more kids going to school in the dark, creating increased safety risks. The International Association of Fire Chiefs also opposes the extension, as they sponsor the program that encourages homeowners to change the batteries in their smoke detectors when they change their clocks. A longer DST may result in dead batteries in smoke detectors.

What do you think? Should DST be extended?

Jun
17
2005

Yesterday, an advisory panel for the Food and Drug Administration (FDA) recommended approval of a drug, BiDil, for heart failure in African-Americans. (The approval was unanimous, although two panel members voted against the racial indication labeling for the drug.) If the FDA follows the panel's advice, BiDil will become the first drug approved for use by patients of a particular race. The drug is a combination of two generic drugs (isosorbide dinitrate-also known as nitroglycerine-and hyrdralazine) that works by increasing the body's concentration of nitric oxide, which widens the arteries and helps the heart function more efficiently. The drug was tested in 1,050 African-Americans last fall. In that study, patients taking BiDil had much better survival rates and were much less likely to be re-hospitalized for congestive heart failure. Dramatic outcomes like this are a good thing, right? Yes. But the idea that a drug be approved for patients of a specific race makes many doctors uncomfortable, and it may also be bad medicine. Jonathan Kahn, a law professor and medical ethicist at Hamline University, said:

"It sends the message that because [the study] was done only in African-Americans that somehow African-Americans are different genetically than everybody else. And that is a very dangerous message to be sending. It's one that doesn't need to be sent in order to bring this drug to market."

Some cardiologists think the reason the drug works so well for many African-Americans may not be a matter of "race" (for which there is no scientific/genetic basis), but is probably related instead to the root cause of their heart failure: African-Americans are more likely to suffer heart failure due to high blood pressure, while whites are more likely to suffer heart failure due to clots caused by heart attacks or atherosclerosis. But some African-American patients do suffer heart failure caused by clots or hardening of the arteries, and some white patients do have heart failure related to high blood pressure. So critics think that the drug should be labeled for use by patients with heart failure caused by hypertension, instead of use by African-American patients. Dr. Gail Christopher, co-chair of the National commission on Health, Genomics and Human Variation, says:

"It would be 'bad science' to label or market this drug as a 'Black' drug. More importantly, race-based claims are not credible in the face of modern genetic medicine."

The New York Times says:

"The drug's maker, NitroMed Inc., says its decision to test and market BiDil as a drug for African-Americans is based on solid science. But BiDil's application [for FDA approval] has engendered controversy, with many scientists convinced that race is too broad and ill-defined a category to be relevant in determining a drug's approval, especially since geneticists have failed to identify a biological divide separating one race from another. Scientists know that different people have different responses to medications, and in some cases these have been linked to race. The FDA, for example, has said that people of Asian ancestry are more likely than others to get serious side effects from the cholesterol-lowering drug Crestor. But research shows that the underlying genetic variations across races are small. [Studies have shown that genetic variation within any racial group exceeds that between two groups.] Scientists believe that genetic markers will someday be found that explain the different reactions to drugs, but for now, race or ethnicity is an imprecise shortcut. By approving BiDil, the FDA would go well beyond where it has in the past in using race as a category to evaluate which patients respond to drugs."

Other doctors feel that failing to take race into account when treating patients is unacceptable. Dr. Jim Kennedy, a spokesman for the Royal College of GPs, told the Times:

"To close one's eyes to colour is tantamount to a neglect of clinical duties. As a practicing professional, I took an oath not to pay any attention to a patient's race, creed, colour or background, and I take this very seriously. But if there is real evidence that because of your genetic inheritance you should be offered a certain drug, I would be negligent in not offering it to you. There may be people of African descent who will benefit from ACE inhibitors, but trying to guess what genes someone has inherited in impossible. So doctors make a reasonable stab at a first-choice drug and if it doesn't work we'll use our second choice. I think it's far worse if, for reasons of political correctness, we chose to ignore real, hard scientific facts."

What do you think about the prospect of race-based medicine? Should drug companies be marketing to specific ethnic groups? How is this harmful or helpful?