In this question, we are not provided with the data that is necessary in order to answer it. Therefore, we cannot know what the age distribution of prehistoric Native Americans was. However, we can give you an explanation of the concepts that will allow you to answer this question on your own.
First, you need to get the mean age expressed in years. The mean is the value you get after adding up the values of all terms and dividing them by the number of terms. The sample variance is the average of the squared differences from the mean. Finally, the standard deviation is the measure of how spread out the numbers are. It is also the square root of the variance.