How do scientists date dinosaur bones?

You’ve seen them in the magazines, on television, in the museums and maybe you’ve even held one in your hands. We’re talking about dinosaur bones. A question that often arises is “How do scientists determine the age of a dinosaur bone?” That’s what we’ll briefly explore in this month’s article.

Certain things in life seem obvious. We know, for instance, that fire is hot, the moon orbits the Earth and chocolate ice cream is much better than plain vanilla. Something else that most would consider being obvious is that dinosaur bones are millions of years old. Most scientists believe them to be at least 65 million years old. That’s one of the things that make them so fascinating to most people. To be holding or looking at something that lived millions of years ago… very intriguing and mysterious!

However, have you ever asked yourself or anyone else, “What is it about a dinosaur bone that makes it so old?” In other words, what about the bone itself makes it old? I’ve asked many people that question and the response is usually a short period of silence followed by the shrugging of the shoulders.

Now, I know that we are all taught from kindergarten on up that dinosaurs roamed the Earth for 150 million years and died out about 65 million years ago. There’s no question that this is what is taught in our public schools and universities. But once again, how do we know the bones are that old? Obviously, the scientists have highly technical dating methods that they use to date the bones. They must put them in a fancy machine and then, “ding” (just like a microwave oven) the timer goes off and tells them how old they are. Right? Wrong! The scientists don’t even date the bones themselves. Wait a minute, I thought they used Carbon-14 dating. This leads me to share a quick personal story… My daughter, Tori, had a biology class last year as a Freshman. She had been raised in a Christian school, but now was in the public school system for her high school years. The topic of dinosaurs came up one day and another student asked “How do they figure out how old the bones are?” to which the teacher replied, “They use Carbon-14 dating.” My daughter, 14 at the time, raised her hand and said, “You do know that the half-life of Carbon-14 is 5,730 years, so there wouldn’t be any Carbon-14 left in the bones if they were millions of years old.” The teacher was stunned and responded awkwardly as if he knew that, but didn’t address the apparent age dilemma. He had to be thinking to himself, “How in the world does a 14 year old girl know the half-life of Carbon-14?”

So do they actually use the Carbon-14 dating method on dinosaur bones? Never, because Carbon-14 dating decays away at a rate that there wouldn’t be any left if the bones were millions of years old (as my daughter so aptly pointed out). In fact, there wouldn’t be any left if the bones were even close to 100,000 years old. However, as mentioned in last month’s article (“DNA in dinosaur bones?”), we actually do find Carbon-14 still in dinosaur bones (even after ruling out potential contamination), which would indicate they are not millions of years old.

So how do they determine the age of the bone? More specifically, where do the millions of years come from?

Typically what happens is that the scientist in the dating laboratory asks where the bone was found (i.e. what layer of the Earth). This gives them an idea of about how old the bone “should be”. How does that work? Well, if the layer is 70-100 million years old (according to their evolutionary beliefs), then the fossils they find in it should be somewhere in that range. But how do they know how old the layers are? Good question! Scientists often tell how old the layers are by determining how old the fossils are that they find in them! Wait a minute… that’s circular reasoning! You’re right, but that doesn’t stop them from using this logic. It’s even in school textbooks. One page will tell about how old the fossils are, using the age of the layers and then a few pages later, state that the age of the layers are determined by the age of the fossils contained in them!

Here’s another approach. Before we had any radiometric dating techniques, ages were assigned to the layers (in the geologic column). This became the standard for determining ages for all the fossils.

If the layer where the fossil was discovered is claimed to be somewhere between 70-100 million years old (based on the previously “assigned age”) then the fossil must be in that range as well. So now that we actually do have radiometric dating, do they then date the rock in which the fossil was found? Seems logical, but the answer is “no.” Fossils are found in sedimentary rocks which cannot be dated by radiometric techniques. So what do they do? They typically date nearby igneous rocks that are above and below the sedimentary layer where they found the fossil. However, what often happens is that the various methods they use (Uranium-Lead, Potassium-Argon, Rubidium-Strontium, etc.) yield widely ranging dates. Remember, the fossil “should be” somewhere between 70-100 million years old (according to their pre-established ages for the geologic column). Perhaps the Uranium method yielded an age of 1.2 billion years. Wow, way too old! That can’t be right. Maybe there was some contamination or something. We can ignore that date. Then the Rubidium method yields 340,000 years. Wow, way too young! Something must have gone wrong with the equipment, so we can throw that date out too. Then, the Potassium method yields 72 million years and they say “See we were right! We thought it was between 70 and 100 million years, we dated it with Potassium-Argon and found it to be 72 million years old.” Then they publish their findings (leaving out the mistaken dates) and the world stands in awe!

This is a clear case of evolutionary bias constricting scientists’ openness to what would seem obvious to most other people… that the bones are not really millions of years old. There was another example regarding an incredible discovery of thousands of dinosaur bones in northern Alaska that were almost completely “fresh”, meaning that there was hardly any fossilization (permineralization). The discoverers did not even report it for 20 years, because they had the look and feel of old cow bones and assumed they were probably just bison, not dinosaurs! (They were thinking that they couldn’t be dinosaur bones, because after millions of years, they would be completely fossilized, but these seemed fairly “fresh”.)

Much more could be said about this, but the moral of the story is that what we are taught about dinosaurs, especially how old they are, doesn’t fit well at all with what we actually observe using good science. What we actually observe, however, fits very well with the biblical account of creation. No surprise to those of us who believe in the inspiration and inerrancy of Scripture!

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Author: Jay Seegert (Co-Founder & Principal Lecturer, Creation Education Center)

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