Info

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Kenyapithecus

Dryopithecus

Graecopithecus

Pongo

Gorilla

Sahelanthropus K. platyops K. rudolfensis H. habilis H. ergaster H. sapiens Australopithecus P. walkeri P. boisei P. robustus Garhi

Praeanthropus

Anamensis

Ardipithecus

Figure 5.3 ► Majority-rule typology, two steps beyond consensus (see text for details).

3 steps (i.e., 390), resulting in the tree shown in Figure 5.4, from 2,096 possible trees. This tree confirms the previous topologies, the only exception being that Praeanthropus is now shown to share a last common ancestor with Sahelanthropus, the garhi group, and more derived hominins (or to interpret it another way, its relationship to these hominins is now unresolved).

To further test these relationships, a bootstrap analysis was generated requesting 1,000 runs. The tree generated is shown in Figure 5.5. This topology is similar to those previously generated. The only difference in the position of the later hominids is that Ardipithecus and the anamensis group now share a sister-group relationship to the exclusion of all other hominids. Following this, we observe the emergence of Praeanthropus, followed by the garhi group. Sahelanthropus then emerges, followed by Australopithecus. Kenyanthropus, Homo, and Paranthropus share a common ancestor to the exclusion of all other hominids, while Kenyanthropus and Homo share a last

Figure 5.4 ► Majority-rule typology, three steps beyond consensus (see text for details).

Kenyapithecus

Dryopithecus

Graecopithecus

Pongo

Gorilla

Sahelanthropus Praeanthropus K. platyops K. rudolfensis H. habilis H. ergaster H. sapiens Australopithecus P. walkeri P. boisei P. robustus Garhi

Anamensis Ardipithecus

Figure 5.4 ► Majority-rule typology, three steps beyond consensus (see text for details).

common ancestor to the exclusion of Paranthropus. The replication values, however, are not particularly strong for most suggested relationships (to perhaps be expected given that it is a bootstrap analysis), the only exception being the monophyletic status of species within Paranthropus and the sister-group relationship of H. ergaster and H. sapiens.

In all of these analyses, the paraphyletic status of Australopithecus and the monophyletic status of Paranthropus are confirmed (with P. boisei being sister to P. robustus). A Homo clade containing all three species of Homo as well as another containing both species of Kenyanthropus is retained in all analyses. The position of A. africanus, representing a basal hominin to both of these clades to the exclusion of all other taxa, is also confirmed. The position of Sahelanthropus and members of the garhi group remains problematic, though both appear to be more derived in the hominin direction as opposed to being more "primitive" Pliocene hominids.

Figure 5.5 ► Bootstrap analysis with 1,000 replications of all 92 characters (see text for details).

2. Analyses of 52 Characters Preserved in Either S. tchadensis and/or K. platyops

The analyses generated here have removed all characters from the analysis that are not preserved in either S. tchadensis or K. platyops. The forty characters deleted from this analysis are 3, 7, 9, 10, 11, 13, 16, 20, 23, 25, 27, 28, 30, 32, 35, 37, 40, 41, 45, 47, 53, 54, 57, 60, 61, 64, 69, 72, 73, 74, 75, 77, 78, 79, 80, 83, 85, 86, 87, and 92.

The strict consensus tree is shown in Figure 5.6, generated from 20 trees, where tree length = 234; CI = 0.453; RI = 0.601; and RC = 0.272. The emergence of Pan and Ardipithecus is followed by Sahelanthropus, the anamensis group, Praeanthropus, the garhi group, and the basal members of the Paranthropus clade and the expanded hominin clade all sharing a common ancestor. Paranthropus forms a monophyletic group, while

Kenyapithecus Dryopithecus Pongo Gorilla Pan

Sahelanthropus Anamensis Praeanthropus K. platyops K. rudolfensis H. habilis H. ergaster H. sapiens Australopithecus Garhi P. waikeri P. boisei P. robustus Ardipithecus Graecopithecus

Figure 5.6 ► Strict consensus tree of 52 characters (see text for details).

the "australopithecines" are paraphyletic. Australopithecus is basal to the Kenyanthropus and Homo clades.

The 50% majority-rule consensus was generated by increasing the tree length by one extra step, resulting in 52 possible trees (Figure 5.7). The emergence of Pan and then Ardipithecus is followed by the garhi and anamensis groups as well as Sahelanthropus and Praeanthropus, all sharing a common ancestor (or unresolved), with a clade containing the Paranthropus lineage, and the more derived hominins, including Australopithecus. All of the percentage replication values can be considered robust. As in previous analyses, Australopithecus is sister to the two sub clades containing Kenyanthropus and Homo, and the replication values are strong for this clade (100%). The same strong support is also provided in the values of the Paranthropus clade (100%). The next analysis increased the tree length by two additional steps, resulting in the generation of 1,619 possible trees (Figure 5.8). This scheme

Figure 5.6 ► Strict consensus tree of 52 characters (see text for details).

Figure 5.7 ► Majority-rule typology, one step beyond consensus (see text for details).

Kenyapithecus

Dryopithecus

Pongo

Gorilla

Sahelanthropus Anamensis Praeanthropus K. platyops K. rudolfensis H. habilis H. ergaster H. sapiens Australopithecus P. walkeri P. boisei P. robustus Garhi

Ardipithecus Graecopithecus

Figure 5.7 ► Majority-rule typology, one step beyond consensus (see text for details).

is the same as that just discussed, the only difference being slightly reduced replication values (to be expected). The last analysis increased the tree length by three additional steps, resulting in the generation of 8,000 likely trees. The consensus tree for this analysis is shown in Figure 5.9. The only difference in this tree from those discussed previously is the repositioning of Ardipithecus to the unresolved status of Sahelanthropus, Praeanthropus, and the garhi and anamensis groups. Again the replication values are relatively robust.

Figure 5.10 represents the bootstrap analysis (1,000 replications) generated on the 52 characters preserved in either Sahelanthropus and/or K. platyops. This analysis seems to confirm the more derived status of Sahelanthropus and Australopithecus, but with very low footstrap values.

All of these analyses confirm the paraphyletic status of the australop-ithecines, while supporting the monophyletic status of Paranthropus

Majority-rule typology, two extra steps beyond consensus (see text

Kenyapithecus

Dryopithecus

Pongo

Gorilla

Sahelanthropus Anamensis Praeanthropus K. platyops K. rudolfensis H. habilis H. ergaster H. sapiens Australopithecus P. walkeri P. boisei P. robustus Garhi

Ardipithecus Graecopithecus

Figure 5.8 i for details).

Majority-rule typology, two extra steps beyond consensus (see text species. The expanded Homo clade is retained, with H. habilis being placed as a basal member of Homo. Australopithecus is maintained as representing the basal group from which Kenyanthropus and Homo emerge. The phylo-genetic position of the other Plio/Pleistocene hominids remains largely unresolved, and their phylogenetic relationship to the hominins is obscure.

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