It is speculation. An analysis of small channels in fossil and modern skulls suggest that humanlike speech abilities arose more than 400,000 years ago. They are inferring things about vocal cords, intelligence, and culture, based on someone s opinions about the functionality of small channels in a skull. Then they infer age using other criteria. Inference is Not Reliable Inference is not as reliable for determining truth as experimentation is.
Inference is merely someone s opinion.
That opinion could be influenced by prejudice, a desire for fame, or the need to satisfy a sponsor to obtain more funding. One can infer just about anything, regardless of the truth. Evolutionists have made some ridiculous inferences. For example, it can be shown experimentally that mutation causes genetic information to be lost. From that they infer that mutation causes genetic information to be gained, too.