Stories tagged evidence

Yup, still not Friday, but posting a few Science Friday videos that I've missed lately.

Science Friday
Science FridayCourtesy Science Friday

From 3/25,

"Artist Angela Strassheim began her career as a forensic photographer in a crime lab. She soon left to focus on art full-time, but she didn’t entirely leave the field behind. Her body of work, Evidence, is a documentary art project created using forensic techniques she learned on the job. The striking, sometimes disturbing images ask the question: after a tragic event, what remains?"
Jan
02
2009

Archaeologists excavate mass graves in Iraq.
Archaeologists excavate mass graves in Iraq.Courtesy US Army Corps of Engineers, St. Louis District and Regime Crimes Liaison Office
It’s the last weekend to go check out the CSI exhibit which takes visitors through the process of gathering forensic evidence and solving a case and the January issue of Archaeology magazine offers a really interesting look at how forensic techniques can be used on a large scale. It follows the role of American archaeologists in gathering evidence used in the trial of Saddam Hussein and other leaders for the 1988 mass murder of Kurdish people in Iraq.

Investigators had many documents suggesting the previous Iraqi leaders were guilty of genocide and had found what looked like mass graves. However, they looked to excavating the graves and locating the bodies in order to prove that the previous Iraqi government had targeted a civilian population of a particular ethnicity.

Mobile camp to analyze remains and artifacts
Mobile camp to analyze remains and artifactsCourtesy US Army Corps of Engineers, St. Louis District and the Regime Crimes Liaison Office
A team of archaeologists from the U.S. Army Corps of Engineers surveyed the desert and found 10 burial pits all oriented in the same direction. They uncovered one of the pits and photographed it. Then they removed each body with its clothes and belongings one at a time, marking each one’s position. They made a case file for each victim and analyzed each individual’s clothing, bones, and DNA samples to reconstruct what had happened.

I was shocked to read that of the 114 people they found, 84 were children. From the belongings people had with them, the team thought that the victims expected to be relocated but were instead led into a one of 10 already dug pits and shot.

The archaeological evidence was used in court along with government documents and eyewitness accounts including the testimony of a man who had survived the massacre. Hussein had been sentenced to death in another trial, but five of the other six defendants were convicted.

The team of archaeologists stayed to excavate and return the bodies to Kurdish officials, who held a reburial ceremony and plan to use some of the objects for a holocaust museum.

Oct
06
2008

Do you often find yourself watching those prime-time crime dramas on TV asking yourself, "Wow! I didn't know they could figure out whom the killer is based on a single carpet fiber sample found on the sidewalk outside of a crime scene! Can they really do that?!?" Well, some of the processes we see on TV may not be quick as quick and easy, or even possible compared to real life crime investigation.

Lisa Smith, of the University of Leicester School of Psychology, is doing some research to see how these portrayals of forensics on TV are affecting how jurors view forensic evidence in actual court cases. Jurors make their decisions based upon their knowledge, perceived understanding, and beliefs regarding forensic evidence. So the next time you are watching some evening television or even hear a news story regarding some forensic evidence, think twice about the validity of what you see!

Oh, and if you like, there is an online questionnaire for the study!

http://www.survey.bris.ac.uk/leicester/evidence

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.