Were humans present on earth during the ice age?
Yes, they were.The last major ice age ended about 10,000 years ago. Anatomically modern humans have existed for about 100,000 years.During the ice age, two distinct species of humans coexisted, homo sapiens (modern humans) and homo neanderthalensis (Neanderthals). There is evidence that both species were present in Europe and Asia, and evidence that homo sapiens were present in North America as early as 13,500 years ago, maybe earlier.There is a large body of evidence of humans preying on large ice age animal populations, including bones with weapon marks, in garbage pits or even utilitarian items made from animal bones and teeth. Some experts believe these large animal populations, like the mastadons , mammoths, and giant sloths were decimated by efficient human hunting.A prevailing theory states humans migrated to the North American continent by a land bridge in the Bering Straits created by the lowered sea levels due to the large ice sheets.Cosquer Cave, a paleolithic cave art site in France, is situated 120 feet below sea level. The paintings are from 27,000 years ago, and the cave would have been accessible during that time due to the decreased sea levels. The paintings show a number of extinct animals, like the megaloceros deer, as well as ibex, seals and great auks.There is no question that humans existed during the last ice age.
If the Earth is 4.5 billion years old and humans have only been around for a few hundred thousand years, how do we know there have not been many more civilizations and species before us?
The Universe is 13.7B years old. The Earth has not existed since the moment the Universe was created and is about 4.5B years old and is made out the debris of two previous generation of stars.Life on Earth started shortly after the temperatures cooled down, about 3.7B years ago. Up until 600M years ago, life was predominantly single-celled organisms. From 600M years until now, the variety of life that we see evolved.Humans started to separate from the rest of the great apes about 7M years ago and we became modern humans 200k years ago.Life has immense complexity and we don't see species arising multiple times. It's just incredibly unlikely. Like a [math]10^{-500}[/math] chance -- like winning the lottery 100 times in a row. This would never happen even if there was an Earth-like planet around every star in the Universe, with the entire population of human-like creatures playing the lottery once every second for the entire age of the Universe (past and present).But there is a very reasonable question about how much we know about the period of time in between when life formed and 600M years ago. Could there have been multiple cycles of complex life that then collapsed back down to single cell life? After all, that's 3B years, 5 times longer than this last period when we went from single celled organisms to us (evolving trees, fish, flowers, multiple epochs of dinosaurs, mammals and yes, humans). From my reading, we have pretty strong evidence against this. The evidence is in chemical traces of life that we use to infer the existence of old life. If there had been vast boom-bust cycles we would see more variety in these chemical markers for life both varying in locations around the globe and also in the depth (which is a proxy for time).When you start thinking about what needs to be done to take a hot rock that's a lot like a global volcano and turn it into the pristine environment that we see, you realize that it takes a lot of time. The atmosphere and oceans were toxic to modern multicellular life and early life had to separate out all the nasty chemicals. This took a lot of time. Even so, it certainly seems like life took its sweet time and then got in a huge hurry over the past 600M years.
What is the estimated age of mankind on earth?
The cleanest answer is that we’ve been making civilizations for about 6,000 years, Homo Sapiens have been around for about 200,000 years, and our most recent ancestors walked the Earth about 6,000,000 years ago.[1]Human evolution is an interesting subject because it’s not as rigid as one might think it is. Since we are all individuals caught in time, there’s no way to exactly pinpoint when “mankind” began. I reckon that since evolution is such a slow, gradual process, the lineage between Homo Sapiens and our ancestors blends together.2.5 million year old tools found in Gona, Ethiopia.[2]The common stereotype is that cavemen (i.e. primitive Homo Sapiens) learned how to control fire. However some scientists hypothesize that our relative Homo Erectus might’ve mastered fire-making about 1.5 million years ago.[3] Neanderthals made tools, and might’ve even created their own language.[4] Those seem like very human-like characteristics for two species that are taxonomically different than us.Once you start applying evolutionary biology to Humanity’s prehistory, the lines begin to blur, and things get interesting.Footnotes[1] How Long Have Humans Been On Earth? - Universe Today[2] 2.5-million-year-old stone tools from Gona, Ethiopia[3] Why Scientists Argue About Which People Mastered Fire[4] Neanderthal behavior - Wikipedia
How did the Earth exit ice ages in the past?
Snowball EarthExtreme climate reversal began to occur 750,000,000 years ago. There were at least four cycles of brutal ice ages between 750 mya and 580 mya. The only life on this planet were microbes living in the ocean. Cyanobacteria were the dominate life form on Earth releasing large amounts of oxygen. Oxygen is capable of combining with methane and removing it as a hothouse gas. In addition, rainfall (over millions of years) scrubs heat-trapping carbon dioxide out of the air. The reduction in these hothouse gases allows global temperatures fall.Large ice packs begin to form. White ice reflects more solar energy than the darker seawater, driving the temperature even lower and creates an unstoppable cooling effect that will engulf almost the entire planet in ice. Cyanobacteria under the ice begin a massive die off. Underwater volcanos continue to release the greenhouse gas, carbon dioxide. The muddy bottom sediments on the ocean floor continue to release the greenhouse gas, methane. These greenhouse gases are trapped under the ice and cannot reach the atmosphere.Million of years pass.Volcanoes sticking their heads above the ice continue to emit carbon dioxide. Slowly, the level of carbon dioxide increases and the earth begins to get warmer. After tens of millions of years, there is enough carbon dioxide to create a greenhouse effect. The ice begins to melt. Cracks in the ice release the trapped methane and carbon dioxide. The earth becomes even warmer. Rain not snow begins to fall. The earth is becoming a warm, wet place.Earth 730 million years ago was a hot, wet planet. Millions of years pass and the earth is beginning to cool again. Increased rain removes carbon dioxide from the atmosphere. Cyanobacteria have recovered in the warm water and are producing more oxygen. Oxygen removes methane and rain removes carbon dioxide from the atmosphere. The temperature on the earth’s surface begins to fall.Ice begins to form in the ocean and the process of cooling and warming begins again. The cycle of extreme hot and cold is repeated at least three more times.The continents continue to drift and the equator becomes mostly water. The equatorial oceans absorb the suns heat better than land, keeping the planet warm. A frozen planet is no longer possible.There will be other ice ages, but the waters at the equator will never freeze again and glaciers will never advance further south than New York.Source: Earth's History
How old was "student-Earth" when modern humans evolved?Say if the earth is 20 years old now.?
How old was "student-Earth" when modern humans evolved? * infant (< 1 year) toddler (age 3) third-grade (age 8) teenager (age 12) high school sophomore (age 15) high school senior (age 17) a few months ago last week yesterday a few hours ago
Matching Pairs Math? Like Grains of sand, Earth's Age, kinda weird one...?
Match each quantity below with the number which represents a reasonable estimate, each of the following match with one of the lines below,?? 1.25X10^(-3) 5X10^(-5) 4.5X10^9 10^10 7.5X10^18 The number of grains of sand in the world — The number of neurons in the human brain — The age of the Earth in years — The weight of a feather in pounds — The width of a human hair in meters — Thanks
How do scientists think they know the age of the earth?
Since the earth doesn't have a date on it, how do scientists think the earth is over billions of years old? I've even seen an approximate date given before, like 8.6 billion years. How could they possibly know this? A human can't know the past if he wasn't there.