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Below are my attempts to describe the evolution of the human hand. A disordered WIP. Fama Clamosa (talk)

"Hands" of a Javanese tree shrew and a human




Analogous forelimb skeletons of three flying vertebrates:
pterosaur, bat, and bird
Primate feet



Phylogenetic studies suggest that a primitive autonomization of the first CMC joint occurred in dinosaurs some 365 million years ago; that a real differentiation appeared approximately 70 million years ago in early primates; and that the shape of the human thumb CMC finally appears about 5 million years ago. This evolutionary process has resulted in the human CMC joint being positioned at 80° of pronation, 40° of abduction, and 50° of flexion in relation to an axis passing through the 2nd and 3rd CMC joints. [6]

Tetrapods

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Tetrapod limbs have five segments: propodium, epipodium, mesopodium, metapodium, and phalanges. The manus and pes are composed of the last three of these.
General name Forelimb Hind limb
Propodium humerus femur
Epipodium radius, ulna tibia, fibula
  Manus Pes
Mesopodium carpals tarsals
proximal series radiale
intermedium
ulnare
tibiale
intermedium
fibulare
medial series centralia (4) centralia (4)
distal series carpalia (5) tarsalia (5)
Metapodium metacarpals (5) metatarsals (5)
Phalanges phalanges (5) phalanges (5)

[7]

[8]

Mammals

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What can be more curious than that the hand of man, formed for grasping, that of a mole for digging, the leg of a horse, the paddle of the porpoise and the wing of the bat, should all be constructed on the same pattern and should include similar bones and in the same relative positions.

Charles Darwin, On the Origin of Species

All mammals limbs are based on the pentadactyl limb as an versatile template. [9] In most mammals the primary function of the forelimbs is locomotion, but in others, including primates, cats, and bears, speed and stamina have been sacrificed for an increased range of motion and a wider range of uses -- in turn, providing increased manual dexterity.

In ungulates, hoofed mammals, the forelimb is optimized for speed and endurance by a combination of length of stride and rapid step -- the proximal forelimb segments are short with large muscles, while the distal segments are elongated with less musculature. In two of the major groups of ungulates --Perissodactyla and Artiodactyla-- what remain of the "hands" --metacarpal and phalangeal bones-- are elongated to the extent that they serve little use beyond locomotion. [10]

The terminal phalanges of Chimpanzees are disproportionately small with little apical tufting. [11]

Ungulates

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Fetlock

In the horse, an example of an odd-toed ungulate Perissodactyla, the forelimb has a single third metacarpal bone equipped with a large metacarpophalangeal joint (fetlock) featuring two posterior sesamoid bones (like in the human thumb). The large proximal and intermediate phalanges end in a specialized terminal phalanges surrounded by the hoof -- a thick derivative of the claw. Likewise, the giraffe, an Artiodactyla and the largest even-toed ungulate, has large terminal phalanges and fused metacarpal bones able to absorb the stress from running.

In even-toed ungulates whose habitats do not require high-speed running over hard terrains, other arrangements of the digits are common. For example, in the Bush Pig (Potamochoerus porcus) the third and fourth toes are weight-bearing, but their non-weight-bearing second and fifth toes are positioned more posteriorly.

Hippopotamus -- four weight-bearing metacarpals. [12]

Cats

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Among the cats designed for speed and strength rather than stamina. short limbs, more muscles distally with greater ranges of motion in the wrist than ungulates. costly limb anatomy. more varied agility -- swat prey, climbing, grooming [13]

Plantigrade

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The plantigrade sloth bear, an insectivorous carnivore, has distal forelimbs resembling feet with carpals arranged similar to the tarsal bones in human feet. However, unlike most mammals, the sloth bear fifth metacarpal is the longest and resembles the human fifth metatarsal. [14]

Three-toed sloth

In the Red Panda, the forelimb digits are also oriented forward but resemble human hands more than the sloth bear. ... feeding behaviour, bamboo. Large radial sesamoid bone reminiscent of opposable thumb

Meerkat, vestigial first digits, MC 2-4 long claws

Sloth, order Pilosa, hang upside-down from branches, highly specialized third and fourth digits (unable to walk on the ground, drags body with claws), short and squat proximal phalanges with much longer terminal phalanges, vestigial second and fifth metacarpals, palm extends to distal IP joint. [15]

Primates

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Volar surface of right hand of large monkey

Potto

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Potto hand

Lorids have reduced index fingers. In species such as Perodicticus potto and angwantibo, the index fingers are vestigial, but these arboreal, nocturnal primates can still grip branches with their opposable thumbs. [16]

The third and fourth digits are connected to each other by a slight skin fold, as are the proximal third of toes 3–5. [17]

Hominoidae

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Hominoid taxonomy (history)
Hylobatidae/Gibbons
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White-handed gibbon

Asian apes are highly suspensory and have highly mobile ball-and-socket midcarpal joints poorly adapted for weight-bearing. Their hands show many hand features directly related to their locomotor repertoires that are likely uniquely derived yet independently acquired within Pongoidae and Hylobatidae. In orangutan the lunate is expanded radioulnarly, the triqutrum is reduced, the pisisform isprojecting distally, the joint between the trapezium and second metacarpal is expanded palmarly, and the phalanges are highly curved. In hylobatids, the thumb CMC is similar to a ball-and-socket joint.[18]


Siamang
[edit]
Hylobates lar : As is well known, gibbons possess a ball and socket joint at the base of the thumb metacarpal, with the convex (male) surface being located on the trapezium. There are reasonable grounds for assuming that this is a secondary specialization and the joint surface on the first metacarpal may show suggestive indications of derivation from the sellar shape typical of other hominoids. Indeed, as noted above, some specimens of Pongo pygmaeus show a significant approach towards the hylobatid form. As in the pongids described, an anterior oblique ligament is present and a strong posterior oblique ligament radiates from a bony dorsal tubercle on the trapezium.

[20]

Fused digits of a siamang

In one species of gibbon, the large Symphalangus syndactylus ("joined-fingers fingers-together"), the second and third toes have extensive skin folds that tightly joins the two toes into a single functional unit. Similarly, Gorillas often have digits 2–5 in both their hands and feet joined by skin folds. [21]

Hominidae/Orangutan

[edit]
Orangutan hook grip

In Pongo pygmeus, the surfaces of the CMC are "typically and unequivocally" saddle-shaped, but in other cases the trapezium's ventral overhang might be reduced or swollen; the latter case resembling the condition in gibbons (trapezium surface convex, ball-like). Posterior and anterior oblique ligaments are present, but no "specialized lateral ligament". Capsule is "overlaid laterally by the bony prepollex receiving part of the insertion of the tendon of abductor longus pollicis." [20]

Homininae/Gorilla

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A small thumb


The joint surfaces of the gorilla CMC are saddle-shaped like in human hands and the surface on the trapezium is wider than in chimps, approaching the condition in human hands. The gorilla trapezium has a "striking and unique specialization": adjacent to/behind the dorsal tubercle is a "massive bony apophysis [...] mimicking it"; it extends proximally to form a "supernumary articulation with the tubercle of the scaphoid." "It seems likely that the bony process is derived from the prepollex, and, on occasion, may persist as a separate bony element." [20]

Hominini/Chimps

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Bonobo "fishing" for termites. Weak thumb grip without opposition.

Pan and homo lineages diverged about 5-7 million years ago, and chimpanzees, genetically our nearest living relative, closely resemble the most ancient hominid fossils from that time.

Chimpanzee hands have elongated fingers, metacarpals and carpals with small, weak, and relatively immobile primate thumbs. The third and fourth metacarpals absorb the largest compressive forces during knuckle-walking, and are the most robust bones in the chimpanzee hand. To withstand stresses during arboreal locomotion, the proximal and intermediate phalanges are curved towards the palm. In contrast to the broad human apical tufts, the tips of the chimpanzee fingers are cone-shaped. In the palm, a transversal skin crease reflects the equally arranged metacarpophalangeal joints. The bones of the thumb are slender and short and the thumb muscles intrinsic to the hand are small.

Chimpanzees use a hook grip for suspension from horizontal supports, and a diagonal hook grip with vertical supports. When the thumb is in contact with the support it fails to squeeze the surface against the palm, and while this grip is used for flailing with sticks, the hand tend to lose its grip when the arm swings forward, mostly due to the weak thumb and its inability to overlap the index finger. [2]

The articular surfaces in the chimp CMC are saddle-shaped like in humans, but the surface on the trapezium is less broad. The palmar surface of the trapezium faces almost directly medially. The posterior and anterior oblique ligaments are also similar but the latter is "of flimsier texture". There are no lateral [carpometacarpal] ligament; where on might have expected it a thin fibrous capsule is covered by the insertions of the abductor pollicis longus tendon. [20]

Pan-Homo LCA
[edit]
Something in common (1906)
Hominid evolution
Non‑<br />hominid primates
Cladogram of hominid evolution based on post-molecular phylogeny[23]

There is no fossil representative of the Pan-Homo last common ancestor, but the morphology of this LCA can be inferred from parsimony and hypothesis about phylogenetic relationships between living and extinct primates. Before molecular data was introduced, it was assumed that great apes and humans formed separate clades (i.e. human linage thus pre-dating the LCA of great apes), a concept based on the interpretation of morphological similarities as shared derived characters (synapomorphy) rather than shared primitive characters (symplesiomorphy). At first glance, the hands of the great apes can indeed appear more similar to each other than to those of modern humans, and, for example, in 1970 Napier proposed that the hands of gorillas and chimpanzees are far to specialized to be ancestral to human hands, and that they thus had "no bearing on the evolution of the human hand". However, substantial molecular and morphological evidence suggests that Pan and Homo are more closely related to one another than either is to Gorilla and that these three are more closely related to one another than either is to Pongo. Furthermore, the same evidence indicates that the Pan-Homo LCA existed 8-4 mya, the African apes-Homo LCA 10-6 mya, and a LCA including Orangutan some 18 mya. [24]

A parsimonious interpretation of the present hominid phylogeny indicates that the hand morphology of all extant great apes are homologous. Hand features shared by Pongo and African apes, but not non-hominids primates, were present in the hands of the Hominidae-Homininae LCA. Shared upper limb features related to suspensory behaviours can be homoplastic, and if so, inferences regarding some of the hand features of the Hominidae LCA would require adjustment. Parsimony and many phenetic similarities between modern human hands and those of African apes (rather than Asian apes) suggests it is more likely the hand of the Pan-Homo LCA resembled that of an African ape. [24]

Pre-bipedal locomotor mode -- whether the Pan-Homo LCA was a terrestrially adapted knuckle-walker or a primarily arboreal climber/clamberer...

[...]

17 osteological features most likely present in the hands of the Pan-Homo LCA[25]
Thumb and fingers
Feature Non-hominid
primates
Pongo Gorilla Pan Homo
Finger length relative thumb   Long     Short
Shape of proximal phalanges   Curved
dorso-
palmary
    Straight
Shaft of proximal phalanges
Flexor sheaths
  Robust
Marked
    Gracile
Weak
Apical tufts of distal phalanges Narrow       Broad
First metacarpal Gracile       Robust
Wrist and carpometacarpal joints
Feature Non-hominid
primates
Pongo Gorilla Pan Homo
Scaphoid and os centrale Separate
bones
Fused      
Surfaces of CMC in opposable thumb   Strongly curved     Weakly curved
Art. surf. of trapezium on scaphoid
extends onto scaphoid tubercle
No       Yes
Orientation of CMC 2/trapezium joint radio-ulnarly       proximo-distally
Trapezoid Wedge-shaped       Boot-shaped
Art. surf. of scaphoid on trapezoid Triangular, large       Rectangular, small
Art. capitate-trapezoid Dorsal, smaller       Palmar, larger
Capitate neck "Waisted"
(on radial side)
      Expanded
(on radial side)
CMC 2/capitate joint orientation radio-ulnar       proximo-distal
Styloid proc. at 3rd MC base Absent       Large
Midcarpal joint (capitate-hamate) Narrower Broader      
Pisiform shape Longer, rod-shaped       Shorter, pea-shaped


Homo

[edit]
Human hand length proportions are largely plesiomorphic, in the sense that they more closely resemble the relatively short-handed Miocene apes than the elongated hand pattern of extant hominoids. The human complex repertoire of manual grips is possible thanks to human intrinsic manual proportions, i.e. a long thumb relative to the rest of the hand. On the contrary, extant apes possess relatively long hands with a short thumb, in which the musculature is poorly developed.

[28]





Further reading
  • McHenry, Henry M. (1983). "The capitate of Australopithecus afarensis and A. africanus" (PDF). American Journal of Physical Anthropology. 62 (2): 187–98. doi:10.1002/ajpa.1330620208. PMID 6418011. In overall shape the bones are more like H. sapiens than other extant hominids, although they are uniquely different. The two A. afarensis capitates provide no evidence that there are two postcranial morphotypes at Hadar. Available evidence shows that A. afarensis and A. africanus are strikingly similar postcranially. The morphological differences between the capitate of Australopithecus and H. sapiens may relate to the retention of climbing ability and an absence of certain grip capabilities in these early hominids.
  • Susman, RL (May 6, 1988). "Hand of Paranthropus robustus from Member 1, Swartkrans: fossil evidence for tool behavior". Science. 240 (4853): 781–4. doi:10.1126/science.3129783. PMID 3129783. New hand fossils from Swartkrans (dated at about 1.8 million years ago) indicate that the hand of Paranthropus robustus was adapted for precision grasping. Functional morphology suggests that Paranthropus could have used tools, possibly for plant procurement and processing. The new fossils further suggest that absence of tool behavior was not responsible for the demise of the "robust" lineage. Conversely, these new fossils indicate that the acquisition of tool behavior does not account for the emergence and success of early Homo.

Additional images

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See also

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Notes

[edit]
  1. ^ Bouissac 2004, p. 4
  2. ^ a b Young 2003
  3. ^ Marzke, Massey University
  4. ^ "Human Evolution: Tools, hands, and heads in the Pliocene and Pleistocene". Encyclopædia Britannica. Retrieved December 2009. {{cite web}}: Check date values in: |accessdate= (help)
  5. ^ Tocheri et al. 2008
  6. ^ Brüser, Gilbert & Brunelli 1999, p. 167
  7. ^ Thies, Monte L. "The Appendicular Skeleton". Sam Houston State University. Retrieved May 2010. {{cite web}}: Check date values in: |accessdate= (help)
  8. ^ Hyman, Libbie Henrietta; Wake, Marvalee H. (1992). Hyman's Comparative Vertebrate Anatomy. University of Chicago Press. ISBN 9780226870137.
  9. ^ Gough-Palmer, Maclachlan & Routh 2008, p. 510
  10. ^ Gough-Palmer, Maclachlan & Routh 2008, p. 582
  11. ^ Gough-Palmer, Maclachlan & Routh 2008, p. 583
  12. ^ Gough-Palmer, Maclachlan & Routh 2008, p. 504
  13. ^ Gough-Palmer, Maclachlan & Routh 2008, p. 505
  14. ^ Gough-Palmer, Maclachlan & Routh 2008, p. 507-8
  15. ^ Gough-Palmer, Maclachlan & Routh 2008, p. 508-9
  16. ^ Burton & Burton 2002, pp. 2034–5
  17. ^ Ankel-Simons 2000, p. 340
  18. ^ Tocheri et al. 2008, p. 546
  19. ^ Susman 1979
  20. ^ a b c d Lewis 1977, pp. 160–61
  21. ^ Ankel-Simons 2007, p. 342
  22. ^ Kivella & Schmitt 2009
  23. ^ Tocheri et al. 2008, p. 546
  24. ^ a b Tocheri et al. 2008, pp. 545–6
  25. ^ Tocheri et al. 2008, pp. 546, 548
  26. ^ a b Lovejoy et al. 2009, pp. 101–102
  27. ^ Lovejoy et al. 2009, Abstract
  28. ^ Almécija, Moyà-Solà & Alba 2010
  29. ^ Flanagan & Johansson 2002, hand Movements
  30. ^ Frey 2008
  31. ^ Bouissac 2004
  32. ^ Peeters et al. 2009

References

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Almécija, Sergio (2009). "Evolution of the hand in Miocene apes: implications for the appearance of the human hand (PhD Thesis)" (PDF). Universitat Autònoma de Barcelona. {{cite journal}}: Cite journal requires |journal= (help)
Almécija, S; Moyà-Solà, S; Alba, DM (2010). "Early Origin for Human-Like Precision Grasping: A Comparative Study of Pollical Distal Phalanges in Fossil Hominins". PLOS ONE. 5 (7): e11727. doi:10.1371/journal.pone.0011727. PMC 2908684. PMID 20661444.
Ankel-Simons, Friderun (2000). "Hands and Feet". Primate anatomy: an introduction. Academic Press. pp. 300ff. ISBN 0120586703.
Bouissac, Paul (2004). "Gestures in Evolutionary Perspective" (PDF). Open Semiotics Resource Center. Retrieved March 2010. {{cite web}}: Check date values in: |accessdate= (help)
Brüser, Peter; Gilbert, Alain; Brunelli, Giovanni R. (1999). "Stability in the first carpometacarpal joint". Finger bone and joint injuries. Taylor & Francis. ISBN 1853176907.
Burton, Maurice; Burton, Robert (2002). International Wildlife Encyclopedia (3rd ed.). Marshall Cavendish. pp. 2034–2035. ISBN 0761472665.
Flanagan, J Randall; Johansson, Roland S (2002). "Hand Movements". Encyclopedia of the human brain (PDF). Elsevier Science.
Frey, Scott H (2008). "Tool use, communicative gesture and cerebral asymmetries in the modern human brain". Philosophical Transactions of the Royal Society B: Biological Sciences. 363 (1499). Phil. Trans. R. Soc. B: 1951–1957. doi:10.1098/rstb.2008.0008. PMC 2606701. PMID 18292060. {{cite journal}}: Unknown parameter |month= ignored (help)
Hartwig, Walter Carl (2002). The primate fossil record. Cambridge University Press. ISBN 0521663156.
Gough-Palmer, Antony L.; Maclachlan, Jody; Routh, Andrew (March 2008). "Paws for Thought: Comparative Radiologic Anatomy of the Mammalian Forelimb". Radiographics. 28 (2): 501–10. doi:10.1148/rg.282075061. PMID 18349453.{{cite journal}}: CS1 maint: date and year (link) (PDF)
Kivella, Tracy L.; Schmitt, Daniel (2009). "Independent evolution of knuckle-walking in African apes shows that humans did not evolve from a knuckle-walking ancestor". PNAS. 106 (34): 14241–14246. doi:10.1073/pnas.0901280106. PMC 2732797. PMID 19667206. {{cite journal}}: Unknown parameter |month= ignored (help)
Lewis, O J (April 1964). "The homologies of the mammalian tarsal bones". J Anat. 98 (Pt 2): 195–208. PMC 1261275. PMID 14154422.{{cite journal}}: CS1 maint: date and year (link)
Lewis, O J (February 1977). "Joint remodelling and the evolution of the human hand". J Anat. 123 (Pt 1): 157–201. PMC 1234261. PMID 402345.{{cite journal}}: CS1 maint: date and year (link)
Lovejoy, C. Owen; Suwa, Gen; Simpson, Scott W.; Matternes, Jay H. (October 2009). "The Great Divides: Ardipithecus ramidus Reveals the Postcrania of Our Last Common Ancestors with African Apes". Science. 326 (5949): 73, 100–106. doi:10.1126/science.1175833. PMID 19810199. S2CID 19629241. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)CS1 maint: date and year (link)
Marzke, MW; Marzke, RF (July 2000). "Evolution of the human hand: approaches to acquiring, analysing and interpreting the anatomical evidence". J Anat. 197 (Pt 1): 121–40. doi:10.1046/j.1469-7580.2000.19710121.x. PMC 1468111. PMID 10999274.{{cite journal}}: CS1 maint: date and year (link)
Marzke, Mary. "Evolution of the hand and bipedality". Massey University, NZ. Retrieved December 2009. {{cite web}}: Check date values in: |accessdate= (help)
Marzke, Mary (1999). "Evolution of the hand and bipedality". In Lock, Andrew; Peters, Charles R. (eds.). Handbook of human symbolic evolution. Wiley-Blackwell. ISBN 0631216901.
Peeters, R.; Simone, L.; Nelissen, K.; Fabbri-Destro, M. (2009). "The Representation of Tool Use in Humans and Monkeys: Common and Uniquely Human Features". The Journal of Neuroscience. 29 (37): 11523–11539. doi:10.1523/JNEUROSCI.2040-09.2009. PMC 6665774. PMID 19759300. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
Putz, RV; Tuppek, A. (November 1999). "Evolution of the hand". Handchir Mikrochir Plast Chir. 31 (6): 357–61. doi:10.1055/s-1999-13552. PMID 10637723. Retrieved December 2009. {{cite journal}}: Check date values in: |accessdate= (help)CS1 maint: date and year (link)
Susman, Randall L. (1979). "Comparative and functional morphology of hominoid fingers". American Journal of Physical Anthropology. 50 (2): 215–36. doi:10.1002/ajpa.1330500211. PMID 443358.
Schwartz, Jeffrey; Yamada, Tadasu K. (1998). "Carpal Anatomy and Primate Relationships" (PDF). Anthropological Science. 106 (Supplement): 47–65. doi:10.1537/ase.106.Supplement_47.
Tocheri, Matthew W.; Orr, Caley M.; Jacofsky, Marc C.; Marzke, Mary W. (2008). "The evolutionary history of the hominin hand since the last common ancestor of Pan and Homo". J. Anat. 212 (4): 544–562. doi:10.1111/J.1469-7580.2008.00865.X. PMC 2409097. PMID 18380869. (Abstract, PubMed) (PDF, Smithsonian)
Young, Richard W (January 2003). "Evolution of the human hand: the role of throwing and clubbing". Journal of Anatomy. 202 (1): 165–74. doi:10.1046/j.1469-7580.2003.00144.x. PMC 1571064. PMID 12587931.{{cite journal}}: CS1 maint: date and year (link) PDF