How old is the Earth?

[Janus58]

But I did read that they trace human skulls with carbon 14 and claim the prehistoric humans existed hundreds thousand years ago.

As already stated carbon dating is only used to 50,000 years ago. So they only use it to date skulls younger than that. Other methods are used to date older skulls.
In other words, yes they do use carbon dating when tracing some skulls, but this doesn't mean that they use it to date all skulls.

 

[sculptor]

But I did read that they trace human skulls with carbon 14 and claim the prehistoric humans existed hundreds thousand years ago.

Where did you read that?

 

[James R]

But I did read that they trace human skulls with carbon 14 and claim the prehistoric humans existed hundreds thousand years ago.

Carbon 14 has a half life of 5730 years, which means that it isn't particularly useful to date things that are much older than several times that period. Carbon 14 is just fine for tracing back over the period of all recorded human history however, so it's very useful in archeology.

Dating human skulls that are 100,000 years old is very unlikely to use a method based on carbon 14.

We know approximately how long modern humans have been around from lots of other dating methods. For instance, we have the fossil record and analysis of DNA.

 

[exchemist]

But I did read that they trace human skulls with carbon 14 and claim the prehistoric humans existed hundreds thousand years ago.

Either you misunderstood or your source was a very bad one.

Why don't you check any of this for yourself? It is all on Wikipedia. And for a lecturer in mechanics like you, it should be easy to understand.