Masses : 1, g in 1 kg; 1, kg in 1 tonne. For example : tonne mass of a blue whale; million tonnes of global human biomass.
Power and energy : 1 watt of power uses 1 joule of energy per second; about watts in 1 horsepower; 3, kilojoules kJ or kilocalories kcal in 1 kWh of energy, sustaining 1, watts for 1 hour. For example , a watt incandescent light bulb illuminates a room; 80 watts sustain human basal metabolic rate, using 6, kJ or 1, kcal or 1. Patrick Doncaster , 7 November , one of the then 7,,, rising by per minute, 79 million per year.
Evolution of life on Earth 4,,, earliest life on Earth: single-celled prokaryotic Archaea Hadean Eon , 3. While our ancestors have been around for about six million years, the modern form of humans only evolved about , years ago. Civilization as we know it is only about 6, years old, and industrialization started in the earnest only in the s. The effects of humans on Earth cannot be understated.
Every year, we fell forests and destroy other natural areas, driving species into smaller areas or into endangerment, because of our need to build more housing to contain our growing population.
The first tangible link to humanity started around six million years ago with a primate group called Ardipithecus, according to the Smithsonian Institution. Based in Africa, this group began the path of walking upright.
This is traditionally considered important because it allowed for more free use of the hands for toolmaking, weaponry and other survival needs. The Australopithecus group, the museum added, took hold between about two million and four million years ago, with the abilities to walk upright and climb trees. Starting about 65, to 50, years ago, more advanced technology started appearing: complex projectile weapons such as bows and spear-throwers , fishhooks , ceramics , sewing needles.
People made representational art — cave paintings of horses , ivory goddesses , lion-headed idols , showing artistic flair and imagination. A bird-bone flute hints at music. But fossils and DNA suggest that human intelligence became modern far earlier. Bones of primitive Homo sapiens first appear , years ago in Africa, with brains as large or larger than ours.
At this point, humans had braincases similar in size and shape to ours. Assuming the brain was as modern as the box that held it, our African ancestors theoretically could have discovered relativity, built space telescopes, written novels and love songs. Their bones say they were just as human as we are. Because the fossil record is so patchy, fossils provide only minimum dates. Human DNA suggests even earlier origins for modernity.
All living humans descend from those people, suggesting that we inherited the fundamental commonalities of our species, our humanity, from them. All human cultures form long-term pair bonds between men and women to care for children.
We sing and dance. We make art. We preen our hair, adorn our bodies with ornaments, tattoos and makeup. We craft shelters. Humans and their ancestors have been walking the planet for about 6 million years.
Homo sapiens, who are the modern form of humans evolved , years ago from Homo erectus. Human civilizations started forming around 6, years ago. Ardipithecus is the earliest link to humanity dating 6 million years ago. The primate was based in Africa and was the first to walk upright. Bipedalism allowed Ardipithecus to use his hands for weaponry, toolmaking, and survival needs.
Between 2 million and 4 million years ago, the Australopithecus group appeared. This group was more advanced than the Ardipithecus: they could walk upright, create advanced tools, and climb trees.
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