this was to give birth at an early stage of fetal development, before the skull grew too large to pass through the birth canal. Other accompanying adaptations were the smaller maxillary and mandibular bones, smaller and weaker facial muscles, and shortening and flattening of the face resulting in modern-human's complex cognitive and linguistic capabilities as well as the ability to create facial expressions and smile. Consequentially, dental issues in modern humans arise from these morphological changes that are exacerbated by a shift from nomadic to sedentary lifestyles. This adaptation enabled the human brain to continue to grow, but it imposed a new discipline. It is to be noted that traditional claims about men's and women's gender roles have been challenged in the past years. Regardless, humans' increasingly sedentary lifestyle to protect their more vulnerable offspring led them to grow even more dependent on tool-making to compete with other animals and other humans, and rely less on body size and strength. About 200,000 years ago Europe and the Middle East were colonized by Neanderthal man, extinct by 39,000 years ago following the appearance of modern humans in the region from 40,000 to 45,000 years ago. History of humans In the Late Pliocene, hominins were set apart from modern great apes and other closely-related organisms by the anatomical evolutionary changes resulting in bipedalism, or the ability to walk upright. Characteristics such as a supraorbital torus, or prominent eyebrow ridge, and flat face also makes Homo erectus distinguishable. Their brain size substantially sets them apart from closely related species, such as H. habilis, as we can see an increase in average cranial capacity of 1000 cc. Compared to earlier species, H. erectus developed keels and small crests in the skull showing morphological changes of the skull to support increased brain capacity. It is believed that Homo erectus were, anatomically, modern humans as they are very similar in size, weight, bone structure, and nutritional habits. Over time, however, human intelligence developed in phases that is interrelated with brain physiology, cranial anatomy and morphology, and rapidly changing climate and environments. Tool-use The study of the evolution of cognition relies on the archaeological record made up of assemblages of material culture, particularly from the Paleolithic Period, to make inferences about our ancestor's cognition. Paleo-anthropologists from the past half-century have had the tendency of reducing stone tool artifacts to physical products of the metaphysical activity taking place