He argues that a deeper understanding of the human environmental footprint will also have practical consequences, helping us recognize better ways to achieve a long-term balance with the planet so we don't end up as tomorrow's forgotten species. The moon is a favored target of Penn State University astronomer Jason Wright, one of a handful of other researchers now applying serious scientific thinking to the possibility of pre-human technological civilizations.
If so, artifacts of their technology, or technosignatures, might be found elsewhere in the solar system. Wright suggests looking for such artifacts not just on the lunar surface, but also on asteroids or buried on Mars — places where such objects could theoretically survive for hundreds of millions or even billions of years. Finding technosignatures in space is an extreme long shot, but Wright argues that the effort is worthwhile.
These advances enabled humans to spread into new, more complex environments, such as coastal locales, and eventually across the entire planet. But symbolic thinking may not account for all of the changes in the human mind, says Thomas Wynn, an archaeologist at the University of Colorado. Wynn and his colleague, University of Colorado psychologist Frederick Coolidge, suggest that advanced "working memory" was the final critical step toward modern cognition.
Working memory allows the brain to retrieve, process and hold in mind several chunks of information all at one time to complete a task.
Yet there are artifacts that do seem to relate to advanced working memory. Making tools composed of separate pieces, like a hafted spear or a bow and arrow, are examples that date to more than 70, years ago. But the most convincing example may be animal traps, Wynn says.
The only plausible way to capture such critters was with snares and traps. With a trap, you have to think up a device that can snag and hold an animal and then return later to see whether it worked. It may be too simple to say that symbolic thinking, language or working memory is the single thing that defines modern cognition, Marean says. He suggests bringing people into a psych lab to evaluate what cognitive processes are engaged when participants make and use the tools and technology of early humans.
Another area that needs more investigation is what happened after modern cognition evolved. The pattern in the archaeological record shows a gradual accumulation of new and more sophisticated behaviors, Brooks says. But in the modern origin story, evolution, there's no defining moment of creation.
Instead, humans emerged gradually, generation by generation, from earlier species. Just like any other complex adaptation — a bird's wing, a whale's fluke, our own fingers — our humanity evolved step by step, over millions of years.
Mutations appeared in our DNA, spread through the population, and our ancestors slowly became something more like us and, finally, we appeared. People are animals, but we're unlike other animals. We have complex languages that let us articulate and communicate ideas. We're creative: we make art, music, tools.
Our imaginations let us think up worlds that once existed, dream up worlds that might yet exist, and reorder the external world according to those thoughts. Our social lives are complex networks of families, friends and tribes, linked by a sense of responsibility towards each other.
We also have an awareness of ourselves, and our universe: sentience, sapience, consciousness, whatever you call it. And yet the distinction between ourselves and other animals is, arguably, artificial. Animals are more like humans than we might like to think. That's especially true of the great apes. Chimps, for example, have simple gestural and verbal communication. They make crude tools, even weapons , and different groups have different suites of tools — distinct cultures.
Chimps also have complex social lives, and cooperate with each other. As Charles Darwin noted in The Descent of Man , almost everything odd about Homo sapiens— emotion, cognition, language, tools, society — exists, in some primitive form, in other animals. We're different, but less different than we think. In the past, some species were far more like us than other apes — Ardipithecus , Australopithecus , Homo erectus and Neanderthals.
Homo sapiens are the only survivors of a once diverse group of humans and human-like apes, collectively known as the hominins. It is a group that includes around 20 known species and probably dozens of as yet unknown species.
The extinction of other hominins, however, has helped to create the impression of a vast, unbridgeable gulf that separates our species from the rest of life on Earth. But the division would be far less clear if those species still existed. What looks like a bright, sharp dividing line is really an artefact of extinction. The discovery of these extinct species now blurs that line again and shows how the distance between us and other animals was crossed — gradually, over millennia. Our lineage probably split from the chimpanzees around six million years ago.
These first hominins, members of the human line, would barely have seemed human, however. For the first few million years, hominin evolution was slow. It seeks to answer our readers' nagging questions about life, love, death and the Universe. We work with professional researchers who have dedicated their lives to uncovering new perspectives on the questions that shape our lives. If you have a question you would like to be answered, please email either send us a message on Facebook or Twitter or email bigquestions theconversation.
The first big change was walking upright , which let hominins move from forests into more open grassland and bush. But if they walked like us, nothing else suggests the first hominins were any more human than chimps or gorillas. Ardipithecus , the earliest well-known hominin, had a brain that was slightly smaller than a chimp's , and there's no evidence they used tools.
In the next million years, Australopithecus appeared. Australopithecus had a slightly larger brain — larger than a chimp's, but still smaller than a gorilla's. It made slightly more sophisticated tools than chimps, using sharp stones to butcher animals. Then came Homo habilis. For the first time, hominin brain size exceeded that of other apes. We make art.
We preen our hair, adorn our bodies with ornaments, tattoos and makeup. We craft shelters. We wield fire and complex tools. We form large, multigenerational social groups with dozens to thousands of people. We cooperate to wage war and help each other. We teach, tell stories, trade. We have morals, laws. The details of our tools, fashions, families, morals and mythologies vary from tribe to tribe and culture to culture, but all living humans show these behaviours.
That suggests these behaviours — or at least, the capacity for them — are innate. These shared behaviours unite all people. We inherited our humanity from peoples in southern Africa , years ago. Archaeology and biology may seem to disagree, but they actually tell different parts of the human story. Bones and DNA tell us about brain evolution, our hardware. Tools reflect brainpower, but also culture, our hardware and software.
Humans in ancient times lacked smartphones and spaceflight, but we know from studying philosophers such as Buddha and Aristotle that they were just as clever.
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