Human beings are members of a species of hominid, which is the same biological classification that includes the advanced apes like chimpanzees. The earliest hominid ancestor of humankind was called Australopithecus: a biological species of African hominid (note: hominid is the biological “family” that encompasses great apes – Australopithecus, as well as Homo Sapiens, are examples of biological “species” within that family) that evolved about 3.9 million years ago. Australopithecus was similar to present-day chimpanzees, loping across the ground on all fours rather than standing upright, with brains about one-third the size of the modern human brain. They were the first to develop tool-making technology, chipping obsidian (volcanic glass) to make knives. From Australopithecus, various other hominid species evolved, building on the genetic advantages of having a large brain and being able to craft simple tools.
One noteworthy descendent of Australopithecus was Homo Erectus, which gets its name from the fact that it was the first hominid to walk upright. It also benefited from a brain three-fourths the size of the modern human equivalent. Homo Erectus developed more advanced stone tool-making than had Australopithecus, and survived until about 200,000 years ago, by which time the earliest Homo Sapiens – humans – had long since evolved alongside them.
Homo Sapiens emerged in a form biologically identical to present-day humankind by about 300,000 years ago (fossil evidence frequently revises that number - the oldest known specimen was discovered in Morocco in 2017). Armed with their unparalleled craniums, Homo Sapiens created sophisticated bone and stone implements, including weapons and tools, and also mastered the use of fire. They were thus able to hunt and protect themselves from animals that had far better natural weapons, and (through cooking) eat meat that would have been indigestible raw. Likewise, animal skins served as clothes and shelter, allowing them to exist in climates that they could not have settled otherwise.
Homo Sapiens was split between two distinct types, physically different but able to interbreed, Neanderthals and Homo Sapiens Sapiens (the latter term means “the wisest man” in Greek). Neanderthals enjoyed a long period of existence between about 200,000 and 40,000 years ago, spreading from Africa to the Middle East and Europe. They were physically larger and stronger than Homo Sapiens Sapiens and were able to survive in colder conditions, which was a key asset during the long ice age that began around 100,000 years ago. Neanderthals congregated in small groups, apparently interacting only to exchange breeding partners (naturally, we have no idea how these exchanges were negotiated - the evidence of their lifestyle is drawn from fossils and archeology).
Homo Sapiens Sapiens were weaker and less able to deal with harsh conditions than Neanderthals, staying confined to Africa for thousands of years after Neanderthals had spread to other regions. They did enjoy some key advantages, however, having longer limbs and congregating in much larger groups of up to 100 individuals. As conditions warmed by about 50,000 years ago they spread to the Middle East and Europe and started both interbreeding with and - probably - slowly killing off the Neanderthals, who vanished by about 40,000 years ago. By that time, Homo Sapiens Sapiens was already in the process of spreading all over the world.
That massive global emigration was complete by about 40,000 years ago (with the exception of the Americas, which took until about 12,000 years ago). During an ice age, humans traveled overland on the Bering Land Bridge, a chunk of land that used to connect eastern Russia to Alaska, and arrived in the Americas. Later, very enterprising ancient humans built seagoing canoes and settled in many of the Pacific Islands. Thus, well before ancient humans had developed the essential technologies that are normally connotated with civilization, they had already accomplished transcontinental and transoceanic voyages and adapted to almost every climate on the planet.
Likewise, the absence of advanced technologies was not an impediment to the attempt to understand the world. One astonishing outgrowth of Homo Sapiens’ brain power was the creation of both art and spirituality. Early Homo Sapiens painted on the walls of caves, most famously in what is today southern France, and at some point they also began the practice of burying the dead in prepared grave sites, indicating that they believed that the spirit somehow survived physical death. Artifacts that have survived from prehistory clearly indicate that Homo Sapiens was not only creating physical tools to prosper, but creating art and belief systems in an attempt to make sense of the world at a higher level than mere survival.