ALL hominoids had more bipedal ancestors:
wading upright + climbing arms overhead in swamp forests:
bipedality does NOT discern "hominin" from other hominids or hominoids.
Apiths were closer relatives of Pan or Gorilla than of Homo.
Most likely,
- E.Afr.apiths (Lucy cs) were a fossil subgenus of Gorilla,
- S.Afr.apiths (Taung cs), of Pan.
Google "aquarboreal".
_______
Op donderdag 6 oktober 2022 om 00:29:44 UTC+2 schreef DD'eDeN aka note/nickname/alas_my_loves:
348B. Wood and M. Grabowski
in light of the recent discovery of the Oligocene catarrhine
Rukwapithecus fleaglei
that may be a basal hominoid (Stevens et al.2014). Langergraber et al. (2012) usedcomparative data about generation times and estimates of mutation rates and con-cluded that the date of the
Pan
–
Homo
split is probably closer to 8 than to 5 Ma, butthe results of a recent analysis of a larger data set (Prado-Martinez et al.2014) thatused different assumptions suggest that it is closer to 5 Ma.Whole genomes can now be sequenced with acceptable levels
of coverage, andin the last few years, researchers have published good-quality draft sequences ofthe genomes of the chimpanzee (TCSAC2005), orangutan (Locke et al.2011),gorilla (Scally et al.2012), and bonobo. Scally et al. (2012) sampled two
westernlowland and one eastern lowland gorillas and showed that when considering theentire genome, the greatest number of similarities is between modern humans andchimpanzees, but in 30 % of the genome, gorillas are closer to modern humansand chimpanzees
than they are to each other. This phenomenon is known asincomplete lineage sorting (ILS). The Prüfer et al. (2012) study showed that bono-bos and common chimpanzees are 99.7 % alike, yet 98.7 % of the bonobo genomeresembles that of modern humans. Prü
fer et al. (2012) also found evidence ofILS in their study to the extent that
c
.3 % of the modern human genome is moreclosely related to bonobos or to common chimpanzees than bonobos and commonchimpanzees are to each other, and they suggest that 25 % of all genes containevidence of ILS. That said, a recent comparative study of 79
great ape genomesrepresenting all six species emphasized that the presence of genetically distinctpopulations within each great ape species (Prado-Martinez et al.2014) confirmsthat despite the effects of ILS, chimpanzees and bonobos are more closely
relatedto modern humans than they are to gorillas. Thus, the comparative context of thehominin clade is the one set out in Fig.1.
3 Criteria for Including Taxa Within the Hominin Clade
The reasons for including the
c
.7 Ma remains assigned to
Sahelanthropustchadensis
(Brunet et al.2002; Guy et al.2005), the
c
.6 Ma remains assignedto
Orrorin tugenensis
(Senut et al.2001), the
c
.5.8–5.2 Ma remains assignedto
Ardipithecus
kaddaba
(Haile-Selassie2001,2004), and the
c
.4.5–4.4 Maremains assigned to
Ardipithecus
ramidus
(White et al.1994,2009; White2010) in the hominin clade, differ according to what anatomical regions arerepresented. However, three common lines of evidence run through the claimsfor the hominin status of these taxa. The first involves a reduction in
size and achange in morphology of the canines, which is linked with the partial or com-plete loss of upper canine/P
3
honing and reduced canine sexual dimorphism. Thesecond involves the location and orientation of the foramen magnum and infer-ences about posture and gait. The third involves features of the pelvis and otherpreserved postcranial elements that imply a
dependence on bipedalism. In eachcase, the assumption is that these character complexes and their inferred behav-iors are
only
seen in the hominin clade.
349Macroevolution in and Around the Hominin Clade
The canine morphology that
Ar. ramidus
and
S. tchadensis
share with laterhominins is the most convincing evidence to support their hominin status. But it isimportant to recognize that during the Late Miocene, a number of Eurasian homi-nids (e.g.,
Oreopithecus
,
Ouranopithecus
, and
Gigantopithecus
) also developedsmaller canines and a reduction in canine–premolar honing. Presumably, thesewere parallel responses linked to analogous shifts in dietary behavior and there isno a priori reason to exclude the possibility that a similar behavioral and
pheno-typic response could have occurred in at least one extinct African hominid clade.The anteriorly positioned and more horizontal foramen magnum seen inmodern humans and later hominins compared to the extant great apes has beenassumed to relate to the
upright posture and bipedal locomotion of the former.However, comparisons with other primates suggest that these features may also belinked with differences in head carriage and relative brain size rather than uniquelywith bipedalism (Strait2001) and the
differences in the position and orientation ofthe foramen magnum seen in bonobos and chimpanzees, and the overlap betweenthe morphology of bonobos and that of
Sahelanthropus
and
Ardipithecus
sug-gests that we should exercise caution before assuming that a relatively anteriorly
Fig. 1
Current consensus of the phylogenetic relationships and splitting times within the great apeclade. The only Asian great ape, the orangutan (
Pongo
), which is likely to have split off from theAfrican great apes
c
.11 million years, diverged into the Bornean (
Pongo pygmaeus
) and Sumatran(
Pongo abelii
) orangs
c
.1 million years ago. There have been two major and two minor splits inthe African ape clade. The first major splitting event, the one leading to gorillas, occurred
c
.8 mil-lion years ago. The second, leading to modern humans, occurred
c
.6 million years ago. The splitwithin gorillas, into mountain (
Gorilla beringei
) and lowland (
Gorilla gorilla
), occurred
c
.2.5 mil-lion years ago. The split within chimpanzees occurred
c
.2 million years ago when the Congo Riverdivided the ancestral chimpanzee population into bonobos (
Pan paniscus
) to the south and commonchimpanzees (
Pan troglodytes
) to the north. The details of the subspecies, along with the timing ofany splits, are more conjectural. Figure courtesy of Adam Gordon. Evidence for the phylogeneticrelationships within the extant great ape genera is drawn from a variety of sources (
Pan
: Groves2005; Gonder et al. 2011;
Gorilla
: Groves2001; Scally et al.2012;
Pongo
: Brandon-Jones et al.2004; Singleton et al.2004; Locke et al.2011; Prado-Martinez et al.2014)
350B. Wood and M. Grabowski
positioned and more horizontal foramen magnum is linked exclusively with theadoption of habitual bipedalism.The postcranial evidence for bipedalism in
Ardipithecus kadabba
mainlyinvolves the morphology of a proximal pedal phalanx (presumed to belong to
Ar.kadabba,
but from an older geological horizon and with no associated craniodentalremains), whereas in
O. tugenensis
, the evidence mainly involves the morphologyof the proximal femur. The case for the femur being that of a committed bipedis much stronger than the case for the pedal phalanx. The claim that
Ar.
ramidus
was a biped is mainly based on highly speculative inferences about the presenceof lumbar lordosis and on a few features of the pelvis and foot, but the claimsare either based on questionable reconstructions, or they involve characters whoselink to
habitual bipedalism has yet to be convincingly demonstrated.Researchers that support hominin status for
S. tchadensis
,
O. tugenensis
,
Ar.
kaddaba
, and
Ar. ramidus
do so on the assumption that within the great apes, caninehoning and bipedalism are
confined
to the hominin clade. We believe that theirassumption is a logical fallacy. For even if all hominins are bipedal and lack caninehoning, the converse proposition–that among the great apes bipedalism and the lossof canine honing are confined to the
hominin clade–is not a logical corollary.How strong are the cases for each of the four taxa being hominins? The argu-ment for including
Ar.
kaddaba
in the hominin clade at the present time is a par-ticularly weak one. Its teeth are apelike, and because of the sparse fossil record,there is not enough evidence to be sure it is a committed biped. As for
O. tugenen-sis
, although the external morphology of the proximal femur is consistent with itbeing bipedal, the evidence from the internal morphology of the femoral neck isequivocal. The morphological evidence that
S. tchadensis
and
Ar. ramidus
shouldbe included in the hominin clade is stronger, but is not compelling for either taxon.In addition, their age is against them being hominins. In the case of
S. tchadensis,
if the more recent splitting
c
.5 Ma times are correct, then if it is
c
.7 Ma it is tooearly for it to be the stem hominin. In the case of
Ar. ramidus
, if both it and the
c
.4.2 Ma
Australopithecus anamensis
are lineal ancestors of later hominins, as itsdiscoverers claim, then there is simply too little time for the cranial and postcranialmorphology of the former to evolve into the latter. Also, if the 3.4 Ma foot with anabducted hallux from the Burtele
locality at Woranso-Mille belongs to
Ar. ramidus
,then the “ancestral” scenario is even less likely. Thus, for these reasons, one of ushas referred to
S. tchadensis
,
O. tugenensis
,
Ar.
kaddaba
, and
Ar. ramidus
as “pos-sible hominins” (e.g., Wood2010) and this is how we refer to them in this review
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