How do scientists know what past climates were like?

Answer: 

Among the major sources of evidence are sediment cores from the ocean bottom. They preserve the fossils of tiny organisms called foraminifera. By measuring oxygen in the skeletons of these organisms, scientists can calculate fluctuations in temperature and moisture over millions of years. Some of the most dramatic climate fluctuations in all of Earth’s history occurred during the period of human evolution.

How do scientists know the age of fossils?

Answer: 

Scientists have developed more than a dozen methods for determining the age of fossils, human artifacts, and the sediments in which such evidence is found. These methods can date objects millions of years old. What’s more, the methods can be tested against one another to provide a highly reliable record of the past. Read more about dating methods here.

Isn’t evolution controversial among scientists?

Answer: 

Evolution is the cornerstone of modern biology. There is no scientific controversy about whether evolution occurred or whether it explains the history of life on Earth. As in all fields of science, knowledge about evolution continues to increase through research and serious debate. For example, scientists continue to investigate the details of how evolution occurred and to refine exactly what happened at different times.

Did humans evolve in a straight line, one species after another?

Answer: 

Human evolution, like evolution in other species, did not proceed in a straight line. Instead, a diversity of species diverged from common ancestors, like branches on a bush. Our species, Homo sapiens, is the only survivor. But there were many times in the past when several early human species lived at the same time.

 

 

How are humans and monkeys related?

Answer: 

 

Humans and monkeys are both primates. But humans are not descended from monkeys or any other primate living today. We do share a common ape ancestor with chimpanzees. It lived between 8 and 6 million years ago. But humans and chimpanzees evolved differently from that same ancestor. All apes and monkeys share a more distant relative, which lived about 25 million years ago.

How does evolution explain complex organisms like humans?

Answer: 

Evolution doesn’t happen all at once, especially in complex organisms such as human beings. Modern humans are the product of evolutionary processes that go back more than 3.5 billion years, to the beginnings of life on Earth. We became human gradually, evolving new physical traits and behaviors on top of those inherited from earlier primates, mammals, vertebrates, and the very oldest living organisms.

What do scientists mean when they call evolution a theory?

Answer: 

Like gravity and plate tectonics, evolution is a scientific theory. In science, a theory is the most logical explanation for how a natural phenomenon works. It is well tested and supported by abundant evidence. It means quite the opposite from our informal use of the word theory, which implies an untested opinion or guess. As a scientific theory, evolution enables scientists to make predictions and drives investigations that lead to new kinds of observable evidence. 

How does evolution work?

Answer: 

To survive, living things adapt to their surroundings. Occasionally a genetic variation gives one member of a species an edge. That individual passes the beneficial gene on to its descendents. More individuals with the new trait survive and pass it on to their descendents. If many beneficial traits arise over time, a new species—better equipped to meet the challenges of its environment—evolves.

How Does Evolution Work

 

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