Skull of Homo erectus
Homo erectus (around 1.8 million years).

Importance of dating

To piece together the story of human evolution, we need to date the pieces.

Every day, archaeologists and palaeoanthropologists are making new discoveries. Each new discovery adds to our knowledge of human evolution and may help to confirm and refine existing theories. But each new discovery also has the potential to challenge the established theories.

In this way, we are continually piecing together our story. An ever-growing story of great breadth and complexity.

The story of human evolution has several important aims. Two of these aims are relevant to our course:

  • Identifying the sequence of physical human development (evolution).
  • Identifying the pattern of migration of the early ancestors of humans (dispersal).

Identifying human evolution and dispersal requires chronological sequencing of the evidence. Chronological sequencing requires dating.

Let’s look at a couple of examples…

Say that we are considering two fossil skulls. One fossil skull has been dated as 60,000 years older than the other. We can now start to identify a few possibilities. Are they of the same species or is it possible that each skull represents an entirely different species? It is possible that one of these species is much older than the other species? The older species could be an ancestor of the younger species. We may dismiss the possibility of the younger species being an ancestor of the older.

Having established the relative dates of the two human fossils, we can now do a couple of things. We can take a close look at the form, shape and structures of the two skulls. This is the morphology of the skulls. Next, we can compare the morphology of the older skull with the morphology of the younger skull. What is similar? What is different? What has changed from one skull to the other?

In this way, we contribute to our body of knowledge on human evolution.

We can also now consider where the two fossils were discovered. For our example, let’s say that archaeologists discovered the older fossil in Africa. But they found the younger fossil five thousand kilometres further north, in Europe. It would now seem probable that the species migrated from Africa to Europe over the millennia.

In this way, we contribute to our body of knowledge on human dispersal.

The chronological sequence allows us to consider ‘who’ and ‘when’. Who was dwelling together, and when were they dwelling together. What if we had discovered both fossil skulls in the same region of Africa? Well, then the story that they told us about human dispersal over 60,000 years would be quite different.

Now take a moment to consider this. Say that the morphologies of the two skulls were very, very different. And that we had discovered both skulls in the same region of Africa. And that we had dated them both to be the same age. What would that tell us? We would now have a very different story to decipher.

Rainer was recently in London, where he caught up with Professor Chris Stringer, from the Natural History Museum. Chris kindly agreed to let Rainer record a series of chats that they had together on the subject of dating fossils, to present to you over this course. In this first video, Chris discusses the importance of dating human fossils.

This is an additional video, hosted on YouTube.

… and scientific methods

By this stage, you may be starting to see that while dating is important to the story - it is not telling us the story. The dating technologies are giving us a calculation of an estimated age range. This calculation has used a particular set of data. These calculations are then used as evidence for the story.

But these calculations do not always fit the established story. What happens when that occurs?

Well, it gives rise to a lot of discussion and debate in scientific circles.

But that’s OK.

This is how scientific methods work. We make observations. We form a theory from those observations. We conduct experiments to test that theory. We then analyse data from these experiments to draw conclusions. Finally, we use these conclusions to change or refine the theory.

Then we test our new theory.

The aim is to reduce the discrepancies between the observations and the theory. As we repeat the experiments we are able to close that gap a little more.

So … can we ever be completely certain about a theory?

No.

This may seem to be a rather frustrating answer at first. But that’s the reality. New discoveries, new technologies and new experiments all have the capacity to challenge any existing theory.

The exciting thing is that we are always making new discoveries.

New discoveries that challenge old stories.

Your task

Think about the question that was posed in this article:

Imagine that we have discovered two Hominid skulls with very different morphologies (physical features). Both skulls had been discovered in the same region of Africa. Both skulls were dated to around the same age.

What might that tell us about their evolution and dispersal?

Select the comments link below and post your response.

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This article is from the free online course:

A Question of Time: How We Date Human Evolution

Griffith University