One of the most important ways in which the rock record supports evolutionary theory is the succession of fossils in older versus newer rock layers. As far back as the 18th century, scholars realized that fossils in older layers differed more from modern life forms than fossils in newer layers. While many fossils from the Pleistocene Ice Age resemble organisms living today, far fewer fossils from the Age of Reptiles do. If you venture back in the rock record to the Precambrian (prior to roughly 550 million years ago), you'll find few fossils of multicellular organisms at all, though you will find some. So striking has this fossil succession been that when asked what would disprove evolution, 20th-century British scientist J.B.S. Haldane quipped, "Fossil rabbits in the Precambrian." No such bunnies have ever been found.
Although scientists differ on the extent of the ice, there is fairly widespread acceptance of the presence of glaciers at sea level at the equator, though some researchers prefer the term Slushball Earth. Many researchers have hypothesized the occurrence of two snowball events: the Sturtian (lasting from about 710 million to 670 million years ago) and the Marinoan (concluding about 635 million years ago.
Science Experiments for Kids: Why do Leaves Change Color
Studies of different human populations indicate that human evolution continued not only after we branched off from apes, but even long after Paleolithic times. Some studies suggest that people whose ancestors came from warm, lowland environments, who had to work hard for all their meals even after food became abundant elsewhere, tend to have slow metabolisms, and people whose ancestors came from cold, highland environments tend to have high metabolisms. While one group had to survive long periods of famine, the other group likely had to metabolize lots of animal fat. What both groups have in common are lifestyle diseases in response to a modern Western diet and sedentary mode of living. There is some debate about whether gene variants leading to type 2 diabetes really resulted from periods of food scarcity ("thrifty gene hypothesis") or whether they just resulted from genetic drift ("drifty gene hypothesis").
Hypothesis in Qualitative Research - ResearchGate
A scientific theory starts out as a hypothesis, a proposed explanation for some phenomenon, and where possible, the hypothesis is subjected to testing. Scientists document such work and publish their papers in peer-reviewed science journals. Other scientists in the same discipline review and comment on the paper before it sees the light of day, and other researchers should be able to replicate the experimental results.
If yes, what are the advantages and limitations
The more scientists examine life on Earth, the more they unravel complex webs of interaction. For example, leafcutter ants feed on a certain type of fungus, and scientists long thought that leafcutter ants kept their fungal gardens pest-free with careful weeding. Then a graduate student discovered that the gardens were under continual threat from a different kind of fungus, a parasitic fungus. He also discovered that the worker ants' abdomens were covered with a substance commonly used in antibiotics. What had long looked like a simple partnership between two species (ants and the fungus they ate) was a more complicated relationship between four species (ants, their fungal food, an annoying fungal pest, and the built-in antibiotic).
The RNA World and other origin-of-life theories. by Brig …
It may even be possible to uncover the effects of epigenetics in human ancestors. DNA degrades over time, but methylated DNA degrades differently from unmethylated DNA, and this finding allowed a team of international researchers to infer chemical tweaks to ancient genes in a 50,000-year-old Denisovan female and a somewhat older Neanderthal female. In April 2014, they announced that gene silencing might account for skeletal differences between modern humans and Neanderthals. Although the results were promising, scientists advised against drawing conclusions from such a small sample.