Name:
Radioactive Dating Problems
Case Study 1: The Oldest Human Ancestor? – Lucy vs. Ardi
Lucy’s Skeleton
Ardi’s skeleton revealed she was 4ft tall and weighed 98 lbs 12 oz
In 1974, Archeologists in Ethiopia discovered a skeleton that they considered to be the oldest human ancestor ever
found. To be precise, the skeleton (Lucy) was discovered to be 3.2 million years old! In 1992, however, scientists
started discovering bones in North East Africa that they thought might belong to an even older human ancestor. For
fifteen years, scientists worked to collect these bones and try to arrange them into a skeleton. The team of scientists
eventually found 125 pieces of bones that they assembled into a new skeleton, which they named Ardi. Scientists
wanted to know who was older, Lucy or Ardi. Scientists were able to use radioactive potassium to figure out how old
Ardi was. The scientists knew that potassium-40 is found in bones, and is radioactive. When potassium-40 decays, it
turns into argon-40. Argon-40 is not radioactive, so it doesn’t decay. This means that over time, the amount of
potassium in the bones will decrease, and the amount of argon will increase. Scientists used this knowledge of the
potassium-argon dating method to determine how old Ardi was.
RESULTS:
Scientists found that Ardi had less potassium and more argon than Lucy.
Who is older?
How do you know?
Case Study 2: The Jesus Wrap? – The Shroud of Turin
Over 700 years ago, people in a small village in France discovered a linen cloth which seemed to have the image of a
man in it. The way the image of this man was visible in the cloth led people to believe that years ago a man had been
wrapped and buried in this cloth, and that as his skin began to rot and decay, it left a print of his image right in the cloth.
Over time, people began to believe that this cloth, which they called the Shroud of Turin, was the actual piece of cloth
that Jesus Christ was wrapped and buried in after he was taken down off the cross. In 1898, a photographer took the
first ever photograph of the cloth and was able to produce a much clearer image of the man’s face. The face did indeed
look like the face of Jesus. For decades people have argued about whether or not the Shroud of Turin really is the cloth
that Jesus was wrapped and buried in. In 1988, scientists were allowed to take a small piece of the cloth to run a
“carbon-dating” test to try and figure out the age of the cloth. Since the cloth is made of organic materials, it has
Carbon in it.
DATA
Scientists found that about 90% of the original C-14 was still remaining. The half-life of C-14 is 5730 years.
How old is the Shroud of Turin?
Is it possible that Jesus was buried in the Shroud of Turin?
Case Study 3: Identifying Victims of the September 11th World Trade Center Attacks.
In the 1950’s, the United States started conducting several nuclear tests around the country. Scientists may not have
properly understood the effects of radiation and of nuclear testing 50 years ago, and in conducting nuclear tests, they
released radioactive atoms into the atmosphere. One of the radioactive atoms released was C-14. Normally, carbondating happens by scientists comparing the amount of C-14 in an object to the amount of C-12 to see how much C-14
has been lost, which tells them how old the object is. This technique no longer works for anyone or any plant that came
into being in the United States after the 1950s, because they have way more C-14 than would be expected because of the
nuclear testing. However, scientists developed what they call “The Bomb Curve,” which shows how much C-14 was in
the atmosphere after each year after the United States started testing bombs. The year that a person was born or that
plant/animal life came into being will determine how much more C-14 is in their cells than there would normally be.
This means that, using The Bomb Curve, scientists can determine the year someone was born, so long as they were born
after 1955.
Billy is a high school student in New York City. In the September 11th terrorist attacks on The World Trade Center,
Billy’s father went missing. Billy and his brother spent ages trying to find their dad and determine whether or not their
dad had died. Many of the victims were too burnt or bruised to easily identify. Billy and his brother eventually find a
man in a hospital who they think might be their father, but they’re not sure. They decide to ask for a carbon dating test
to be done to try and see if it’s possible that this unidentified victim is really their dad.
DATA
Scientists take a small sample of enamel from one of the victim’s teeth, and find that it has 700 times more carbon-14 in
it than would be expected. Billy’s father was born on October 18th, 1958. Is it possible that this man is Billy’s father?
Explain your reasoning!