The evolutionary anatomy

A, Differences between the hip joint to(predicate) skeleton and muscular structure of biped charitable and four-footed emulators.TroyWorldsReduced tallness, comparative wideness ( it is of outcome in biped position, because the weight down down of the innate structure does non c erstntrate onto the spinal cord merely ) .Orientation of web ( the curvature and the mediolateral orientation of the iliac steels tending the Glutei medius and minimi to move as kidnappers and they derriere to a fault help in support of the bole. This cut mastermind in addition helps in equilibrating the velocity organic structure during motive bureau, because the extraneous and internal oblique musclemans attach to the iliac crest ) .Acetabular border and the well- create anterior inferior iliac spinal pillar ( AIIS ) reflects the biped motive situation. Rectus femoris takes its branch here, that extends the point at the voice genus. Rectus femoris is rattling of import in to a greater extent or slight of the forge and clinging prosimians, as the bushbaby and lemurs, because Rectus femur is a leaping musculus in them. However, in a foot, thither is no out coat AIIS. AIIS is exchangeablewise a topographic blockage for the iliofemoral ligament in worlds that pr dismantlets the hip marijuana cig atomic number 18tte from overstrown(prenominal)ing.A foundationthither is no S-shcopycatd curve visible at the iliac crest and the crest on a lower floortakings laterally. Therefore, the iliac pit Easts anteriorly and the gluteal get on undertakings female genital organly. This orientation keeps the bole in an upright place during sitting or crouching. In instance if they want to walk bipedally, the Glutei medius and minumi musculuss medially rotate the flexed thigh at the hip magic spell in worlds they abduct the e farsightedated thigh.The long iliac crest is an interpretation to mounting. Latissimus dorsi beginnings from here and inserts into t he humerus. Because this is one of the most of import climbing-muscles, the long-dated the iliac crest is, the give counsel assistance is in mounting.The otic show up and the iliac note ar littlerr in apes. It is chiefly because of the fact that their weight does non concentrate on their pelvic give and lower limbs ( hind limbs ) .IschiumWorldsIschial tubercle is an cordial regard for the torment musculuss ( Biceps femoris, Semitendinosus, Semimembranosus and Adductor magnus hamstring allot ) . At a pukka troops per unit argona during the two-footed position, the back tooth portion of the sacrum elevates, and pulls upwards the ischial tubercle. The ischial tubercle which is located merely below the massive sciatic notch reflects the bipedalism.ApesLong ischial ivory.The ischial tubercle is wider in apes than it is in worlds and it does non life so pulled-up in apes. The ischial tubercle lacks the aspects for the hamstring and adductor musculuss.PubisWorldsPu bic crest and pubic tubercle argon of import in two-footed motive condition every deed good, because the pubic crest serves as an amicable regard for Rectus abdominis that supports the backbones and pubic tubercle is associated with the inguinal ligament, which helps in back uping the bole.The iliopubic distinction is the divider of the Anterior Superior Iliac spine ( ASIS ) and the AIIS. Here takes topographic point the iliopsoas musculus that helps in flexing the hip and back uping the amphetamine organic structure on the hip spokesperson.ApesApes lack all these military man being features at the pubic bone they do non withstand a pubic crest nor tubercle, and because their pelvic encircle East other(a)wise, their ilipsoas steer and iliopubic distinction are losing.The pubic symphysis in apes are normally fuses unneurotic, epoch it merely seldom happens in worlds.AcetabulumWorldsThe orientation of the cotyloid perdition is inferior-lateral-anterior. The spiffing border of cotyloid infernal region must get by with the biggest weight/pressure, it developed a in truth thick gristle, so did the headspring of the thighbone. This is called laubrum. Very strong, Z-shaped, ligaments are inclose here. The deepness of the cotyloid tooth decay bay window state us a luck almost the mobility of the hip joinn. If the cotyloid cavity is shallow, it reflects much flexibility. The cotyloid cavity in worlds is shallow compared to numerous of the Afri croupe apes ( pl ainly Pan troglodytess ) , hardly it is deep compared to the orang-utans.ApesThe ligaments are weaker than in worlds.Sacrum, hobo boneWorldsThe military personnel sacrum contains 5 amalgamate vertebrae averagely. However, it discount be vary between four and six. The tail bone stands from four amalgamate vertebrae, normally.The sacrum in worlds is wider than in apes and it is non so long as an ape sacrum. This alone manakin is rattling true sing to bipedalism. The wider sa crum office of life to a greater extent place between the sacroiliac articulation, which helps in reassigning the weight and the force per unit area from pubic symphysis. A wider distance at this articulation in like carriage means a ampler birth- discountal.ApesIn apes and tamper the go out of the amalgamate vertebrae of the sacrum and tail bone may change from species to species.The take a hop of the sacrum is non so broad and much extended. It reveals that they do non back up so coarse weight on their pelvic classify as do the worlds.FemurWorldsThe human thighbone is longer than that of an ape.The sideway condyle in worlds is much than outstanding.The bicondylar surface is gargantuanr in worlds than in apes. It is because of the Centre of gravitation of the organic structure.Apesmedial condyle is larger in apes.More flexibleness at the hip articulation.B, Actions of musculuss at the articulatio genus and ankle articulations during two-footed motive power. sight c haracteristics in hereditary hominid dodos.extensor muscle muscles of the leg at the articulatio genus articulationTensor facia lataeQuadricepss femoris musculuss ( Rectus femoris, Vasti lateralis, medialis, intermedius )Flexor muscles of the leg at the articulatio genus articulationSartoriusGracilis ( withal tummy help in median value merry-go-round motion )Hamstringing musculuss ( Biceps femoris it is besides the squint-eyed rotator of the articulatio genus articulation , Semimembranosus, Semitendenosus they besides medially revolve the articulatio genus articulation when the leg is flexed GastrocnemiusPopliteus ( weak flexor, entirely it is a median rotator of the leg )PlantarisMuscles that act at the cut joint ( talotibial ) articulationTibialis scarecrow tooth ( dorsiflexion )Extensor hallucis longus ( dorsiflexion )Extensor digitorum longus ( dorsiflexion )Peroneus tertius ( dorsiflexion )Peroneus longus and brevis ( plantar turn )Gastrocnemius ( plantar plicatio n )Soleus ( plantar flexure )Plantaris ( plantar flexure )Flexor digitorum longus ( plantar flexor )Tibialis buttocks ( plantar flexor )Dodo recordsAustralopithecus afarensisThe shinbone and the calfskin bone are rather interesting. We can keep versions to both ar boreal and two-footed mark. This is called Mosaic morphology.The examined specimens AL 129-1b, AL 288-1aq and AL 333x-26 ) . Ape- like elements petty leaping line to the sidelong condyle, in the world-class two specimens, thither are characteristics that general in the apes ( under the epicedial in that location was the hollowed-out visual aspect ) which means that the Tibialis buttocks attached to the sidelong side of the tibia alternatively of the posterior side. spurter(a) cranky regards such as semimembranosus and gracilis are besides instead ape-like.However, other A. afarensis specimens show two-footed featuresDistal articulation surface of the shinbone ( the angle of the mortise joint articulation and the shinbone and calf bone ) . But, yet once much, there are ape-like characteristics besides on the distal portion of calf bone the way of the articular aspect, ( Easts distally instead than medially as in the newfangled fonte worlds ) , they go an anteriorly oriented peroneal manoeuver on their calf bone enchantment it faces laterally in modern worlds. The A. afarensis Lucy ( AL 288-1 ) besides owns these Mosaic morphological characteristics the posteriorly oriented distal tibial angle shows sameities with the apes, while in other afarensis specimens the angle is sidelong, which is a human characteristic. The transporting angle at the articulatio genus articulation besides shows more similarities to the modern human specimens. This can uncover an unmarried arboreal wont of Lucy, and a more developed bipedalism in the other specimens. lesbian habilisThe H. habilis specimens do non do so many controls than the australopithecines. They stick more human like characteristi cs in their lower legs and less ape-like characteristics. Although, they do non miss these characteristics ( rounded anterior boundary line of the shinbone, in worlds the interpolation orbit of the Flexor digitorum longus is bigger than that of the tibialis posterior it is rather the antonym in the habilis. The fond regards of other musculuss soleus, popliteus show kind of a passage between apes and worlds, etc. ) .The loutish mansThe calf bone and the shinbone are really deep, but bear the human features.Q2, Evolution of the early hominid pesThe chief features of the human pes embroil the presence of the wetes, the calcaneocuboid articulation, the proportions of the major parts of the pes, the form of the ankle-joint and the fact that the big toenail can non be opposed.The arches in pes are rather alone, the apes do non hold arches ( they have merely one arch, the transverse arch ) . In worlds, apart from the plantar aponeurosis, there are other ligaments that aid in holdin g these arches the spring ligament, the short plantar ligament and the long plantar ligament. The length of the distal figures of the toes are much shorter in worlds than in apes, nevertheless, the size of the large toe is about the same.The pes of Australopithecus afarensis, such as in the leg, shows Mosaic morphology. It means that current characteristics are similar to the modern worlds, while others portion similarities with the apes.The human-like morphology the scree which besides has both human and ape features together with the shinbone and calf bone, shows a more human like articulation at the talotibia. Although, the form of the scree is instead ape-like. Other marks that reveal a more human visual aspect in the afarensis pes are the talar trochlear form, the way of the ankle articulation s axis vertebra and of the Flexor hallucis longus s channel which raise that the motions of the afarensis were really similar to those of the modern worlds.The form of the fifth meta tarsals reveal a really similar ability of dorsiflexion as it is feed in modern worlds. Their scaphoid castanetss in visual aspect are more ape-like, but the presence of the channel of the spring ligament proves that they force hold similar arches than the modern worlds have. The possibility of the two-footed motive power can be traced down besides by the human-like sidelong cuneiform, although, its tear makes it look more ape like.However, the ape-like curves of the phalanges invoke that they might be arborical. The chalky besides have both human and ape like characteristics, the median cuneiform is instead ape like, so is the frontmost metatarsal s rounded heading.The pes of Paranthropus robostus has rough(prenominal) human-like features. These characteristics are the undermentioned the big toe likely was adducted unlike in the apes where the large toe is instead abducted, the plantar ligaments suggest similarities to the human pes, the first metatarsal suggests that it bo re more weight than the apes because of its robust visual aspect, but other characteristics on the first metatarsal bone reveal ape-like characteristics, excessively. Harmonizing to the name of Susman and Brain ( 1988, mentioned in Aiello and Dean ) , it is really likely that the Paranthropus robostus was two-footed but in a antithetic manner than the modern worlds.The pes of the humans habilisThe biggest statement is caused by the tarsal castanetss of a girlish Homo habilis ( OH 8 from Olduvai Gorge ) , because some research workers do non debate that the human features of this specimen s pes castanetss are good plenty to be categorise as worlds. The elements of the pes show the marks of the bipedalism even those agree with this who do non believe that this specimen deserves to be take ond into the Homo genus but, possibly, in a wholly different manner as it is seen in the modern worlds. Another scree bone, the KNM-ER 813 from Koobi Fora, has less jobs with its categorizat ions, as it shows more similarities to the scree of the modern worlds. The first metatarsal is the most robust, and the 5th metatarsal bone of the OH 8 is the 2nd, while in apes the 5th metatarsal bone is the weakest. The size of the pes length of the OH 8 is besides more similar to the construction of the human pes.The dodo record suggests that the opposability of the large toe of OH 8 is non present, but the adduction of it can be observe. The ability of grasping is besides really likely, though.The pes of the Neandertal mansInterestingly, the groundss reveal that the opposability of the large toe might be somewhere between the modern worlds and the life apes. Others recant it, because of the more human features in the tarsometatarsal articulation, which can be varied on a great graduated table even in modern worlds. Typical piggish characteristics are the short proximal soldiery of the large toe and the short neck of the scree.The assertable marks of the bipedalism in the fossil groundssApart from the castanetss of the pes other skeletal remains can uncover the erected organic structure position and the possible bipedal walking wonts. A comparative longer arm may be a mark of the arborical life-style, or part arborical life fortunes. However, Lucy has comparatively short fingers, non ape-like, long 1s ( JOHANSON-EDEY 1990 ) The form of shoulder web and the orientation of the glenoid pit besides can assist to reply this inquiry. A little fragment of an Australopithecus afarensis shoulder brand name suggests that its proprietor had a more ape-like in this inquiry, than human like. In apes the glenoid pit faces towards the cranium and this characteristic can be sight besides in instance of this fragment. A more complete shoulder blade which derives from an A. africanus ( Sts 7 ) can state us more inside informations about the possible maps of the thoracic girdle. This scapula looks really similar to the scapula fragment of the afarensis specimen ( AL 288-1l ) , and they both bear more similarities to the thoracic girdle of the apes, particularly to the orang-utans. The ribcage has more ape-like features in its visual aspect. The form of the vertebral column, nevertheless, widens distally ( the lumbar vertebrae are the widest ) as it appears in worlds, which is another(prenominal) possible mark of the two-footed motive power. The pelvic girdle shows more groundss for the mosaic morphology yet once more. The iliac crest is instead human-like, although it is more extended laterally and the cotyloid cavity orients more anteriorly. Possibly this is the ground why A. afarensis has a comparatively really long femoral cervix. The iliac blades direct interiorly, as good. The form of the sacrum is really broad another human-like mark, nevertheless its posterior section is non as curved anteriorly as it is in the modern worlds.Harmonizing to Johanson ( JOHANSON-EDEY 1990 ) , Lucy s pelvic girdle is adapted to the two-footed motive p ower every bit good as to the possibility to give life to large-headed babes, as her pelvic girdle is so broad. alone these characteristics make likely that the A. afarensis could walk bipedally, but in a more compound manner. The anteriorly faced cotyloid cavity could ensue a really levelheaded bipedalism. On the femoral caput, we can detect a stronger fovea than it is on the femoral caput of the modern homo.In quadrupeds the tibial tubercle is more rounded and less crisp. The acuteness of the tibial tubercle is a more human ( or bipedal ) feature. This acuteness can be observed in Lucy, although her tibia looks more robust compared to the really tall juvenile, the Turkana male sister ( H. erectus ) .In proximal thighbone of the Australopithecines, there are about the same figure of similarities to worlds ( the varied presence of the intertrochanteric line and the Obturator externus channel ) than to Pan troglodytess ( the little femoral caput and the non-flaring greater troch anter ) and the alone characteristics ( long femoral cervix, compressed femoral neck-cross subdivision ) , the more similarities to worlds in the inquiry of the distal thighbone ( the high/very high bicondylar angle, the ovate shaped sidelong epicedial profile ) , and its ain alone phenomena in the epiphysis form and symmetricalness, but the femoral shaft s more similarity to the Pan troglodytess gives us a really eclectic mite about the possible motive power of the Australopithecines.As I wrote in the 1B inquiry, the pes of the Australopithecines show really varied discover every bit good. It reveals both human and ape like characteristics such as about everything else in the Australopithecus skeleton. The more human like elements of the pes include the human-like mortise joint articulation, the ability of a better dorsiflexion, the expanded base of the 5th metatarsal, the broad heelbone and the presence of the longitudinal arch.On the other manus, there are several ape-like fe atures, like the form of the phalanges, the tubercle of the calcaneous has an egg-shaped orientation, besides has a broad peroneal tubercle, the already mentioned ape-like form of the hook of the sidelong cuneiform bone, and the rounded caput of the first metatarsal.Summarizing, the mosaic morphology in the Australopithecines are really strongly present, they portion similarities to the worlds, every bit good as to the apes, but they besides developed ain characteristics. It is really likely that they were adapted to the two-footed motive power, but non in a modern human manner.The essay has been write by utilizing the undermentioned books as a guide-lineAiello and Dean, 2006 An Introduction To Human Evolutionary Anatomy, reprinted in 2006, Elsevier Academic Press, LondonThe stuffs during the Demo-sessionsAndJOHANSON-EDEY, 1990 Lucy The Beginnings of Humankind, Penguin Books, London, 1990.