Homo erectus was the first hominid species that scientists consider a direct precursor to modern Homo sapiens sapiens. Most of the other species that came before had significant biological and morphological differences, from spine structure to brain size. Homo erectus walked upright, thus the name "erectus," making them different from other crouched hominids. There were other similarities, making Homo erectus much closer to modern humans than any other ancient hominid; for example, they were one of the first species to consistently use fire for defense and cooking (much of this evidence is disputed). They also had more complex societal interaction, which is where language becomes important; Homo erectus was probably not capable of modern human-like language, but the larger brain capacity allowed common "words" and "phrases" closer to real language than the unformed sounds made by other hominids. This allowed the formation of actual societal groups instead of individuals and harem-societies, and the importance of traits aside from brute strength.