Evolution and carbon 14 dating
This is difficult for some time periods, however, because of the barriers involved in matching rocks of the same age across continents.
Family-tree relationships can help to narrow down the date when lineages first appeared.
There are several different methods for estimating the ages of fossils, including: Paleontologists rely on stratigraphy to date fossils.
"We know from atmospheric measurements over the last 50 years that radiocarbon levels vary through the year, and we also know that plants typically grow at different times in different parts of the Northern Hemisphere.Sedimentary layers: The layers of sedimentary rock, or strata, can be seen as horizontal bands of differently colored or differently structured materials exposed in this cliff.The deeper layers are older than the layers found at the top, which aids in determining the relative age of fossils found within the strata. Such index fossils must be distinctive, globally distributed, and occupy a short time range to be useful.Radiocarbon dating is a key tool archaeologists use to determine the age of plants and objects made with organic material.But new research shows that commonly accepted radiocarbon dating standards can miss the mark -- calling into question historical timelines.