Don't tell Creationist frauds like Ken Ham and Kent Hovind this, but scientists have found a way to extend the accuracy of precision radiometric dating of hominin activity to about 500,000 years - some ten times as far back as carbon-14 dating reliably takes us. It all depended on discarded ostrich shells from the midden tips of our African ancestors!
This holds out the possibility of accurately tracing the progress of our ancestors over time so giving us a more detailed picture of the timing and movement of the different archaic forms as they evolved.
A long and detailed news item from University of California at Berkeley (UC Berkeley) explains how, and the scientists' paper can be read in PNAS, sadly behind a paywall, so only the abstract and statement of significance is freely available.
Explaining the significance of their technique, the Berkeley team say:
From the UC Berkeley News release:Significance
Novel 230Th/U burial dating of ostrich eggshells complements other dating methods applicable to archaeological materials beyond the range of radiocarbon dating. New ages for the Ysterfontein 1 (YFT1) shell midden show it accumulated rapidly between ∼120 to 113 ka closely following the Last Interglacial sea-level highstand. The ages show the great antiquity of intensive human coastal adaptation, date a distinctive lithic industry, and show that teeth from YFT1 are among the oldest H. sapiens fossils recovered in southern Africa. Stable isotopes of ostrich eggshells indicate rapid cooling and drying during site occupation. Despite rapid sea-level drop and increasing aridity, the site’s occupants maintained a consistent diet, which may not indicate a stable paleoenvironment but rather results from systematic, selective foraging.