Humankind's understanding of who we are has expanded enormously in recent decades, but educational institutions are failing to keep up. This applies in spades to the sciences and to historical studies. Our brief human experiment is likely to fail unless all of us more fully understand our planet from the perspective of the 13.8-billion-year history of the universe, and understand our species relative to the fabric of several billion years of biological evolution including 7 million years of human evolution.
Early human "prehistory" is arguably the most inspiring story ever told, and is based upon some of the most fascinating science ever discovered. Nearly all this knowledge has been gained just since the 1920s when we began to understand that humans "diverged" from chimpanzee-like animals in Africa. Incorporating the entire story into K-16 education would vastly expand our knowledge of what it means to be human, yet world history courses still begin with the agricultural revolution a mere few thousand years ago.
The United States is one of the more backward nations in this regard. Until quite recently, polls consistently showed that a majority of Americans still believed humans did not develop from earlier non-human species. Upon mentioning this to a German colleague decades ago, he expressed utter shock at such "medieval" beliefs. By 2020, however, 53 percent of Americans agreed that humans evolved from non-humans, 36 percent believed they did not, while 11 percent were agnostic.
In most other industrialized nations, over 80 percent of the population knows that humans developed from other animals. It's fairly clear that fundamentalist religious beliefs are the source of this frustrating American ignorance. Research shows that science literacy courses at the high school and college level, and especially interdisciplinary "Big History" courses that begin with the Big Bang or with Earth's creation, have played an important role in spreading knowledge among the general public as to how we really got here.
Twenty-three different human (the biological term is "hominin") species have developed since we diverged from the other apes. Most persisted far longer than Homo sapiens, which originated only 300,000 years ago. For example, Homo erectus persisted for 2 million years. The hominin list includes two species living about 6 million years ago, two Ardipithecus species from around 5 million years ago, six Australopithecus species during 4 million to 2 million years ago, three Paranthropus species around 2 million years ago, and finally 10 Homo species including habilis, erectus, neanderthal, sapiens and others during the past 3 million years.
These hominins have been discovered at many different sites all over Africa. Homo erectus seems to have been the first of these to venture outside of Africa. Several sites indicate this species migrated to Europe, the Mideast and Asia during the period from 2 million to 1 million years ago, long before Homo sapiens. They perhaps migrated to the Indonesian islands where they may have evolved into Homo floresiensis, a species of small humans that inhabited the island of Flores until the arrival of modern sapiens about 50,000 years ago. DNA studies of modern people around the world show that sapiens is the sole survivor of the hominin explosion. That is, there has been little mixing of other species such as erectus and neanderthal with modern sapiens.
Two uniquely hominid characteristics are upright walking and large brain development. Apes usually walk on all fours although they can stand on their hind legs. The first hominids could walk bipedally although they mostly swung through the trees. Ardipithecus lived largely in the trees, but it frequently walked bipedally on the ground. Australopithecus lived near open areas, walked upright most of the time, but still climbed trees. It developed the curved spine of modern humans. By the time of Homo, walking was similar to modern humans.
Our amazing brain power developed much later than bipedalism. Ardipithecus' brain volume is only 350 cubic centimeters (cc), slightly smaller than a chimpanzee's brain. A slow evolution of brain size ensues from Australopithecus (450 cc) to Paranthropus (525 cc) to Homo habilis (600 cc), then a more rapid Homo evolution from rudolfensis (735 cc) to ergaster (850 cc) to erectus (1100 cc) to sapiens and neanderthal (both 1350 cc, with neanderthal's brain possibly largest). All this is consistent with Homo tool-making 2.5 million years ago, control of fire 2 million years ago, human burial 80,000 years ago and artistic creativity more than 40,000 years ago.
For further reading, I recommend "Sapiens: A brief history of humankind" by Yuval Noah Harari.