When we are talking of dominance in genes, we have that a gene can present with certain variations, this variations are called alleles. Now acording to mendelian genetics in alleles we can have dominant alleles or recessive alleles.
When an allele is dominant it means thet every time this allele be present the trait thet code will show, it doesn't matter if the organism is homozygous (SS for example) or heterozygous (Ss for example) in both cases the person wil have smile dimples, now a recessive trait will only show itself when is in its homozygous form (ss) and in that case and only the person won't show smile dimples.
The origin of man took place about 200,000 years ago and looking at the records that are stored in the ice cores before the existence of man which were found by the deep drilling of the antarctic and Greenland shows that how the temperatures have changed and as the example of the carbon in the air.
As in the 800,000 years go the Carbon dioxide levels were on average of 170 to 280 ppm and now they have crossed the 400 ppm mark also at that time the sea levels were high as 80 feet and now are more than 100 feet.