Question

how age of fossils can determined

Answer 1

There are two components to this estimation . One is relative . If we dig into the earth and start finding fossils , it is reasonable to suppose that the fossils we find closer to the surface are more recent than the fossils we find in deeper layers . The second way of dating fossils is by detecting the ratios of different isotopes of the same element in the fossil material .

Answer 2

1) It can be determined by relative position of fossils... Fossils present in deep earth layers are older than those present in upper layers...
2) carbon dating method... In this the concentration of isomers of carbon determines the age of fossils.....