Direct dating fossils
In fact, relatively recently the chronology of the level TD4, where the oldest lithic industries of the site were identified, was successfully refined.In TD1, it has likewise been possible to date a level at the base of the sedimentary fillings, where a change of magnetic polarity, identified as the Jaramillo event, was observed: this is very difficult to detect at archaeological sites in caves and it marks a very well-defined moment approximately one million years ago.Heaman and colleagues say their direct dating method can preclude the reworking process that relative chronology entails.It is widely believed that all of the non-avian dinosaurs were wiped out in a mass extinction, known as the KT extinction event, that occurred between 65.6 and 66 million years ago in the late Cretaceous period.Collective work To obtain this dating and overcome the different challenges which arose over the study duration of almost three years, collaboration was needed from specialists in different scientific disciplines such as geochronologists, geologists, archaeologists and paleoanthropologists, among whom are included several researchers from the CENIEH such as Josep María Parés and José María Bermúdez de Castro, coordinators of the program, as well as Laura Martín-Francés and Isidoro Campaña.Researchers attached to institutions based in Australia (Griffith University), Spain (IPHES, Complutense University of Madrid), France (University of Bordeaux) and China (University of Nanjíng), also collaborated.The possibility that dinosaur eggs might survive extreme climatic conditions is also a possible avenue to be explored.
"We used the same special protocol that had previously worked successfully with the fossil remains of Homo naledi and the oldest Homo sapiens found outside Africa" says Mathieu Duval, member of the Geochronology and Geology Program of the CENIEH and now at the Australian Research Center for Human Evolution at Griffith University (Australia) "By combining direct dating of the piece with a new, more precise paleomagnetic study of the deposits of the stratigraphic unit TD6, it was possible to obtain a dating which is consistent with the previous indirect estimates based on the sediment or fauna associated to the hominin remains," the researcher adds.
However, such methods are far from perfect: it is difficult to gain accurate depositional ages for sedimentary rocks, and matters can be further complicated when millions of years of geologic and environmental forces cause erosion of fossil-bearing strata.
Fossils can even migrate from their original positions within strata.
Since the beginning of archaeology, new fossil hominid finds have constantly reshaped our understanding of the human journey.
However, it is often difficult to place these discoveries in their temporal context.
Dating studies on paleoanthropological sites are usually carried out on material associated with the hominin remains, such as the sediment, charcoal or other fauna rather than the hominin specimen itself.