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Originally posted by factfinder38
I guess that I would have to say that I do belive in the evolution of man but I will say that I question some of the conclusions.
When you look at the timeline on the page I supplied there are just so many questions.
orginally from the article linked aboveA few windows are now opening in Africa to glance into the fossil evidence on the earliest hominids, though the picture we have of their anatomy and behavior is still a blur,” said Semaw. “More hominid discoveries are needed from sites such as Gona to fully understand the biological origins of our ancestors.”
Originally posted by factfinder38
It is probably my own simplicity that makes me not understand how they come to such big conclusions from just a few small bones.
Hopefully it was not by position in the fossil record since this would rely on the assumption they are trying to prove for its validity and hence becomes circular logic.
Wouldn't it be nice if media outlets like msnbc would actually provide links to the studies done and their actual data rather than just a pithy summary of it
a selection from the abstract
The hominid dental anatomy (occlusal enamel thickness, absolute and relative size of the first and second lower molar crowns, and premolar crown and radicular anatomy) indicates attribution to Ardipithecus ramidus. The combined radioisotopic and palaeomagnetic data suggest an age of between 4.51 and 4.32 million years for the hominid finds at As Duma. Diverse sources of data (sedimentology, faunal composition, ecomorphological variables and stable carbon isotopic evidence from the palaeosols and fossil tooth enamel) indicate that the Early Pliocene As Duma sediments sample a moderate rainfall woodland and woodland/grassland.
more on the dating from the body of the paper
Dates from two different crystal-rich tuffs (GONASH-51 and GONASH-52) found in the middle of the lower lacustrine interval 14 m below GWM-3 and from the stratigraphically higher basalt flow under GWM-5sw indicate that the deposits are Early Pliocene in age (Fig. 2a, b). The two tuffs were dated by laser fusion 40Ar/39Ar analysis of single plagioclase crystals using methods described previously8 (Supplementary Figs 1 and 2). Excluding the obvious xenocrysts, 23 of 23 (GONASH-51) and 16 of 18 (GONASH-52) plagioclase crystals yielded statistically homogeneous populations with weighted mean ages ( 2) of 4.56 0.23 Myr and 4.59 0.45 Myr, respectively. Although the individual crystal ages are relatively scattered (unweighted population means and standard deviations of 4.45 0.53 Myr (n = 23) and 4.31 0.91 Myr (n = 15) for G-51 and G-52, respectively) their intra-sample homogeneity and variable precision justify the weighted mean as the best estimate for the ages (Supplementary Figs 1 and 2; Supplementary Table 2).
Two samples of groundmass concentrate (WMASH-25 and -27) from the basalt flow beneath GWM-5 were dated by resistance-furnace incremental heating yielding plateau ages of 4.17 0.21 Myr and 4.06 0.39 Myr, with a weighted mean of 4.15 0.18 Myr (Supplementary Figs 3 and 4; Supplementary Table 3). Palaeomagnetic data (referred to the timescale in ref. 9, recalculated for conformity with the standard age used in 40Ar/39Ar dating herein) provide additional constraints on the age of the deposits. The reversed polarity sediments and flows at all sites within these densely sampled stratigraphic sections may have been deposited during a single interval of reversed geomagnetic polarity, given the strong sedimentologic similarities between the GWM-3 and GWM-5 deposits. If this proves correct, the polarity interval that simultaneously satisfies all palaeomagnetic and radioisotopic data is chron C3n.1r with age limits 4.51–4.32 Myr (Fig. 2c). An alternative—but in our view geologically less plausible—interpretation is that GWM-5 is much younger than GWM-3. In this case, the magnetically reversed sediments of GWM-3 belong to chron C3.2r (4.83–4.65 Myr) or chron C3.1r (4.51–4.32 Myr), whereas the magnetically reversed sediments of GWM-5 could conceivably belong to chron C2Ar (4.21–3.61 Myr). In this model, palaeomagnetic constraints would place the GWM-3 block between 4.83 and 4.32 Myr ago, and combined radioisotopic results would place the GWM-5 block between 4.21 and 3.61 Myr ago. Further sampling may clarify the chronological position of GWM-5. The Early Pliocene age for all of these localities is supported by the presence of biochronologically useful species recovered from the hominid sites (for example, Nyanzachoerus jaegeri10, Kolpochoerus deheinzelini11, Anancus cf. kenyensis, Pliopapio alemui12 and Kuseracolobus aramisi12. Another fossil hominid site, GWM-10, although not yet dated geochronologically, is biochronologically indistinguishable from other As Duma localities.
what indicates bipedality
GWM-10/P1 is a nearly complete manual left proximal phalanx probably from ray IV. The GWM-3/P2 manual proximal phalanx, represented by the proximal 40% of the bone, is large. These phalanges are similar in overall morphology to those from Hadar, with two differences: a more transversely broad proximal articular surface and longer absolute length14. The pedal proximal phalanx fragment retains the proximal third of the bone. The transversely broad oval proximal facet is oriented dorsally, a character diagnostic of bipedality and a trait also seen in the latest Miocene hominid Ardipithecus kadabba