Presentación Ardipithecus ramidus.pdf

8/10/2019 Presentacin Ardipithecus ramidus.pdf

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Science 2 October 2009: vol. 326 no. 5949 pp. 71-71e6DOI: 10.1126/science.1175831

235 remains from, at least, 36 specimens,

most of wich belong to an adult female (4.4

Mya)

Ethiopia's harsh Afar desert

Is this species belonged to the branch of

bipedal hominins or left out along with the

Great Apes?


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Fig. 1. Original and reconstructed os coxa of ARA-VP-6/500.(Left)Anterolateral and anteromedial viewsof the original, with a close-up of the AIIS. (Middle) CT

scans of same views, except the bottom view is aclose-up of the pubic symphyseal face, preserved in

its entirety but damaged at its inferior extremity.Arrows indicate major areas of distortion corrected byreconstruction. (Right)Anterolateral and anteromedial

views of the reconstructed os coxa and of the entirepelvis using mirror reconstruction and a conjectural

sacrum.

Illium lateraly flared and has a

forward sweeping anterior

superior iliac spine

Anteriorly positioned anterior

inferior iliac spine is associated

with a broad, short and

sagitally disposed iliac isthmus


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Figure S4. Craniocaudal Pelvic Height and Pelvic Geometry inHominoids. Posterolateral views of the os coxae of hominoids: A) Pan;

B) Proconsul (KNM-MW 13142 D); C)Ar. ramidus; D)Au. afarensis (A.L.

288-1). Two chords are indicated on each specimen: one from the

acetabular center to the most caudal point on the auricular surface

(upper chord), and the other from the acetabular center to the ischialspine (lower chord). Note that the angle between the two chords is most

obtuse in Proconsul and declines in the other taxa but for different

reasons.


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(D) Minimum ischial length (frominferior acetabular border to juncture

of the ischial body and tuberosity

surface) normalized by acetabular

diameter. Two values for ARA-

VP-6/500 bracket possible extremesfor the acetabular diameter. Pan-

Homo d i f ferences are h igh ly

significant.

(C) Angle made by two chordsconnecting three landmarks on the

ilium. The third chord was measured

(auricular surface to the ischial spine),

and the angle was determined

trigonometrically. All early hominids liewithin the human range because all

have a greatly shortened iliac isthmus.


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Figure S5. Relative lateral Iliac Breadth in Anthropoids.

Natural log-log scatterplot of lateral iliac breadth (distance fromthe most lateral point on the auricular surface to the ilium's lateral

margin taken at the location of maximum iliac breadth) and

acetabular height in anthropoids. A regression line (blue: RMA: y

= .485x + 1.573; r = .938; N = 107) has been fitted to the Old

World monkey data, and another of slope equal to one (red) has

been fitted through two points estimated as possible upper and

lower limits of Proconsul (based on KNM-MW 13142 D). Upper

and lower limits of possible acetabular height have been used for

ARA-VP-6/500.

Figure S7. Relative Maximum Iliac Height in Anthropoids. Natural log-

log scatterplot of maximum iliac length and acetabular height in anthropoids.A regression line (blue: RMA: y = .802x + 2.130; r = .876; N = 145) has been

fitted through Old World monkey taxa and another of slope equal to one

(red) has been fitted through Proconsul (KNM-MW 13142 D). Four points

are provided for ARA-VP-6/500 reflecting upper and lower limits for both

dimensions (acetabular height and maximum iliac length). Note that the ilia

of African apes (but not Pongo) appear slightly elongated relative to

Proconsul (distinctly so in Pan), but that hominid ilia are dramatically

shortened. The strong shift made by modern humans largely reflects

enlargement of the acetabulum.


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Figure S10. Correlates of the Trans-Iliac Space in

Hominoids. Viewed anteriorly, the posteromedial edges of

right and left ilia and cranial edge of the sacrum form a "U",the trans-iliac space, indicated here by the horizontal

bracket. It contains and consequently confines the lower

lumbar vertebrae. African apes evidence unique ligaments

between the ilium and these lowest lumbar vertebrae.

Conversely, either broad sacral alae and/or reduction of iliac

height evacuates the trans-iliac space, freeing the lowest

lumbars and enhancing their mobility for lordosis. Specimen

shown here is a female Pan (CMNH-B1758). Gorilla also

exhibits this trait.

Figure S8. Relative Lower Pelvic Height in Anthropoids. Natural log-log scatterplot of

lower iliac height and acetabular height in anthropoids. A regression line (blue: RMA: y =1.052x + .631; r = .791; N = 145) has been fitted through Old World monkey taxa, andanother of slope equal to one (red) has been fitted through Proconsul (KNM-MW 13142D). While Gorilla specimens fall around this line, all of those from Pan fall above it,suggesting that shortening of the back for suspensory locomotion and vertical climbinghas generated spatial compensation by further elongation of the iliac isthmus. Four pointsare provided forARA-VP-6/500 reflecting upper and lower limits for acetabular height andlower iliac height. These points plot close to Proconsul, suggesting maintenance or slightshortening of lower iliac height relative to its dimension in the GLCA. The demonstrableshift from the two early hominids A.L.288-1 and STS-14 to modern humans reflectsseveral effects on lower iliac height by later pelvic evolution, but especially elongation ofthe posterior ilium to increase the sagittal diameter of the birth canal.


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Fig. 4. Lateral and posterior CT scan surface renders of (A)

MAK-VP-1/1 (Au. afarensis, cast) and (B) ARA- VP-1/701 (Ar.

ramidus, original).The preserved portion of the ARA-VP-1/701 shaft

is sufficient to demonstrate the absence of a lateral spiral pilaster and

the presence of a distinct rugose insertion area for the gluteus

maximus that is homologous to the true hypotrochanteric fossa

present in MAK-VP-1/1 (arrows indicate the third trochanter; brackets

indicate hypotrochanteric fossae). In ARA-VP-1/701, this area is

more laterally placed, as in other early hominid femora, including

BAR-1002'00. The more posterior position of this insertion in MAK-

VP-1/1 is almost certainly associated with decreased sagittal iliac

orientation inAu. afarensis, a consequence of further posterior pelvic

broadening and increased lateral iliac flare. None of these early

hominid specimens shows evidence of a lateral spiral pilaster, which

is restricted to African ape femora.

Fig. 2. CT comparison of ARA-VP-6/500 (left) os coxa reconstruction

and A.L. 288-1 (right) restoration. The broad sacral alae of ARA-

VP-6/500 are probably because African ape sacra have almost certainly

been narrowed since the GLCA. A novel ossification center for the AIIS and

a substantial reduction in the height of the iliac isthmus are derived

characters present in both hominids. Spatial orientation was made on an

assumption of vertical alignment of the pubic tubercle and ASIS, although

the primitive form of this pelvis suggests that lumbar lordosis during

terrestrial bipedality was partially situational and that the superior pelvis

may have been angled less anteriorly during arboreal clambering. There is

a dramatic reduction of lower pelvic length and robusticity in A.L. 288-1.


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Figure 1 | Location map. Satellite (AsTER) image

showing study area at Aramis surrounded by modern

Jara and Awash rivers in Afar, Ethiopia, where

Ardipithecus ramidus skeleton was discovered.

Mixed vegetation (woody plants and

grasses) in floodplain environment

Early hominins inhabited riparian

environments, l ikely taking the

advantage of water-fed ecosystems

developed in a narrow forest corridorbordered by more open woody

grasslands

Role of physical environment as a driver

for hominin evolution, including the

development of bipedalism


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Conclusions

Pelvis and femur of Ar. ramidus establish that adaptations

to upright walking were found by 4.4 Mya.

Evidence on the locomotor transition from arboreal life to

habitual terrestrial bipedality.

Presentación Ardipithecus ramidus.pdf

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