The fossil record is based on random elements that survived down to the present for study. DNA studies use blood or saliva from modern people to address evolutionary history, or in rare cases, they can examine the actual DNA of specimens who’ve been found (Wade, 2006). Tools are one category of things that survive well, especially when made of stone. We can confirm that modern humans lived around 170,000 years ago based on the types of tools found with fossilized individuals (Wade, 2006; Olson, 2002). Interestingly, during this period we shared the earth with a population of Neanderthals living in Europe and Western Asia and a population of Homo Erectus people in the Far East and Indonesia (Tattersall & Schwartz, 2000). There were three kinds of human beings, and they all used an identical set of stone tools essentially unchanged for thousands of years (Wade, 2006).
For instance, She regulates women’s menstrual cycles, and when females live together in groups, they tend to synchronize their cycles with each other (Smith, 2007; Diamond, 1992). These people were modern humans, just as intelligent as we are, and I cannot believe they would not have connected the two—especially as fertility was so crucial to the survival of the species.