Paleoecology is a discipline that deals with interactions of fossil organisms in their ancient environments. However, current research indicates that paleoecological data (the fossil record) are inherently different from neoecological data (the present-day world). Due to postmortem processes, such as transport by water currents or reworking by burrowing organisms, skeletal remains of various ages are often mixed together during their fossilization. Thus, in contrast to the living organisms studied by ecologists, individual fossils found preserved together in geological strata are not necessarily contemporaneous. As in human cemeteries, fossiliferous horizons mix together remains of organisms that lived at different times and never interacted with one another. The fossil record tends to be time-averaged.