3.5 billion years ago
4.5 mil
There have been many scientists that have worked on the theory of emergence over the years. Emergence theory has been written about by scientists such as Julian Huxley and John Stuart Miller.
You didn't say what scientists, but science today is built on the contributions of scientists from long ago. There are many examples but prominent among them Is Isaac Newton.
They lacked a definitive answer.
False
Accumulating data, especially proof of sea floor spreading.
Scientists theorize that the first living cells appeared spontaneously. They believe the process took place around four billion years ago.
Human habitation of the Americas began approximately 30,000 years ago
200 million years
The Grey Squirrel is the most common species found in the United States. It has been in the country for around 50 million years and scientists theorize it entered North America through Canada.
By looking at the fossil records, scientists were able to say approximately when life began. They used radiometric dating of rock layers as one method. See links below for further information:
Around 10000 years ago, humans transitioned from a nomadic lifestyle to settled agricultural communities. This shift led to the development of civilizations, the rise of social hierarchies, and the domestication of plants and animals. It marked the beginning of the Neolithic Revolution, which profoundly impacted human society and culture.
It is sometimes considered the "Age of the Mammals".
Most scientists believe that the first early human beings evolved from a species called Australopithecus around two million years ago. This transition marked the emergence of the Homo genus, which eventually led to the development of modern humans.
Scientists have discovered human remains thought to be more than 2 million years older than Lucy, a skeleton found in Ethiopia
Which theory states that Homo sapiens began in a single geographical area and spread out from there
Which theory states that Homo sapiens began in a single geographical area and spread out from there
Scientists who decided it would be a good idea to make a ratio between how long dogs live and how many human years old they are so that humans could compare their dogs age to what a human would act like at that age.