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The hand of Homo naledi.

Kivell TL, Deane AS, Tocheri MW, Orr CM, Schmid P, Hawks J, Berger LR, Churchill SE - Nat Commun (2015)

Bottom Line: Based on associated hominin material, the bones of this hand are attributed to Homo naledi.However, the finger bones are longer and more curved than in most australopiths, indicating frequent use of the hand during life for strong grasping during locomotor climbing and suspension.These markedly curved digits in combination with an otherwise human-like wrist and palm indicate a significant degree of climbing, despite the derived nature of many aspects of the hand and other regions of the postcranial skeleton in H. naledi.

View Article: PubMed Central - PubMed

Affiliation: Animal Postcranial Evolution Lab, Skeletal Biology Research Centre, School of Anthropology and Conservation, University of Kent, Marlowe Building, Canterbury CT2 7NR, UK.

ABSTRACT
A nearly complete right hand of an adult hominin was recovered from the Rising Star cave system, South Africa. Based on associated hominin material, the bones of this hand are attributed to Homo naledi. This hand reveals a long, robust thumb and derived wrist morphology that is shared with Neandertals and modern humans, and considered adaptive for intensified manual manipulation. However, the finger bones are longer and more curved than in most australopiths, indicating frequent use of the hand during life for strong grasping during locomotor climbing and suspension. These markedly curved digits in combination with an otherwise human-like wrist and palm indicate a significant degree of climbing, despite the derived nature of many aspects of the hand and other regions of the postcranial skeleton in H. naledi.

No MeSH data available.


Related in: MedlinePlus

Relative length of the thumb in H. naledi Hand 1.Relative length of the thumb (ray 1, total length of the first metacarpal and first proximal phalanx) and third ray (total length of the third metacarpal and third proximal and intermediate phalanges) within the same individual, in all taxa except A. afarensis (*), for which the ratio is one potential estimate of hand proportions derived from multiple individuals7810. (a) A box-and-whisker plot, where the box represents the 25th and 75th percentiles, the centre line represents the median and the whiskers represent the non-outlier range, of ray 1 to ray 3 length (as a percentage) demonstrates that Hand 1 has a relatively longer thumb than all other hominins, apart from A. sediba, and falls within the upper range of variation in modern human males only. (b) Linear regression of ray 1 length to ray 3 length, with regression line fit to modern humans (males and females combined), shows that Hand 1 (DH1) has a relatively long thumb for its small hand size, falling on the edge of modern human variation. Male and female modern human sample comprises African (n=31), Nubian Egyptian (n=11) and small-bodied Khoisan (n=25) individuals. Data for Shanidar 4 are derived from ref. 17.
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f2: Relative length of the thumb in H. naledi Hand 1.Relative length of the thumb (ray 1, total length of the first metacarpal and first proximal phalanx) and third ray (total length of the third metacarpal and third proximal and intermediate phalanges) within the same individual, in all taxa except A. afarensis (*), for which the ratio is one potential estimate of hand proportions derived from multiple individuals7810. (a) A box-and-whisker plot, where the box represents the 25th and 75th percentiles, the centre line represents the median and the whiskers represent the non-outlier range, of ray 1 to ray 3 length (as a percentage) demonstrates that Hand 1 has a relatively longer thumb than all other hominins, apart from A. sediba, and falls within the upper range of variation in modern human males only. (b) Linear regression of ray 1 length to ray 3 length, with regression line fit to modern humans (males and females combined), shows that Hand 1 (DH1) has a relatively long thumb for its small hand size, falling on the edge of modern human variation. Male and female modern human sample comprises African (n=31), Nubian Egyptian (n=11) and small-bodied Khoisan (n=25) individuals. Data for Shanidar 4 are derived from ref. 17.

Mentions: Modern humans and archaic humans (as represented here by Neandertals) differ from other apes in having short fingers relative to a long and robust thumb with well-developed thenar musculature that facilitates forceful precision and precision-pinch grips between the thumb and fingers456. Most australopiths (for example, Australopithecus afarensis and Australopithecus africanus) have thumb-finger length proportions estimated to be similar to humans789 (but see ref. 10), but with gracile pollical metacarpals (Mc1) that lack strong muscle attachments1112. The almost complete hand of A. sediba MH2 has a gracile but remarkably long thumb, outside the range of variation in recent humans3. Hand 1 also has a long thumb: the first ray length (Mc1+PP1=61.9 mm) is 58% of the third (Mc3+PP3+IP3=107.5 mm), falling only within the upper range of variation in modern human males (mean 55%) and outside the female range of variation (mean 54%; Fig. 2). The curvatures of the pollical carpometacarpal articulation fall within the modern human range of variation, unlike the more curved facets of extant great apes and some other early hominins13. Unlike most australopiths, Hand 1, as well as six additional Mc1 specimens from five other individuals, demonstrate that H. naledi has markedly robust pollical metacarpals with well-developed crests for the opponens pollicis and the first dorsal interosseous muscles (Fig. 3, Supplementary Fig. 1, Supplementary Table 1 and Supplementary Note 1). The former muscle is functionally important for opposition of the thumb to the fingers, as well as holding and manipulating large objects, whereas the latter muscle is strongly recruited during precision and precision-pinch grips14. In H. naledi, the flaring crests on the Mc1 for the intrinsic thenar muscles are accompanied by a prominent palmar ridge running sagittally along the midshaft (Fig. 3). Overall, the well-developed thenar muscle attachments are most similar to those seen in modern humans, Neandertals, and the Swartkrans pollical metacarpals (SK 84 and SKX 5020, attributed to either A. (Paranthropus) robustus or early Homo)151617. In contrast, they are unlike the weakly developed muscle attachments of gracile australopiths31112 and Ardipithecus ramidus18.


The hand of Homo naledi.

Kivell TL, Deane AS, Tocheri MW, Orr CM, Schmid P, Hawks J, Berger LR, Churchill SE - Nat Commun (2015)

Relative length of the thumb in H. naledi Hand 1.Relative length of the thumb (ray 1, total length of the first metacarpal and first proximal phalanx) and third ray (total length of the third metacarpal and third proximal and intermediate phalanges) within the same individual, in all taxa except A. afarensis (*), for which the ratio is one potential estimate of hand proportions derived from multiple individuals7810. (a) A box-and-whisker plot, where the box represents the 25th and 75th percentiles, the centre line represents the median and the whiskers represent the non-outlier range, of ray 1 to ray 3 length (as a percentage) demonstrates that Hand 1 has a relatively longer thumb than all other hominins, apart from A. sediba, and falls within the upper range of variation in modern human males only. (b) Linear regression of ray 1 length to ray 3 length, with regression line fit to modern humans (males and females combined), shows that Hand 1 (DH1) has a relatively long thumb for its small hand size, falling on the edge of modern human variation. Male and female modern human sample comprises African (n=31), Nubian Egyptian (n=11) and small-bodied Khoisan (n=25) individuals. Data for Shanidar 4 are derived from ref. 17.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4597335&req=5

f2: Relative length of the thumb in H. naledi Hand 1.Relative length of the thumb (ray 1, total length of the first metacarpal and first proximal phalanx) and third ray (total length of the third metacarpal and third proximal and intermediate phalanges) within the same individual, in all taxa except A. afarensis (*), for which the ratio is one potential estimate of hand proportions derived from multiple individuals7810. (a) A box-and-whisker plot, where the box represents the 25th and 75th percentiles, the centre line represents the median and the whiskers represent the non-outlier range, of ray 1 to ray 3 length (as a percentage) demonstrates that Hand 1 has a relatively longer thumb than all other hominins, apart from A. sediba, and falls within the upper range of variation in modern human males only. (b) Linear regression of ray 1 length to ray 3 length, with regression line fit to modern humans (males and females combined), shows that Hand 1 (DH1) has a relatively long thumb for its small hand size, falling on the edge of modern human variation. Male and female modern human sample comprises African (n=31), Nubian Egyptian (n=11) and small-bodied Khoisan (n=25) individuals. Data for Shanidar 4 are derived from ref. 17.
Mentions: Modern humans and archaic humans (as represented here by Neandertals) differ from other apes in having short fingers relative to a long and robust thumb with well-developed thenar musculature that facilitates forceful precision and precision-pinch grips between the thumb and fingers456. Most australopiths (for example, Australopithecus afarensis and Australopithecus africanus) have thumb-finger length proportions estimated to be similar to humans789 (but see ref. 10), but with gracile pollical metacarpals (Mc1) that lack strong muscle attachments1112. The almost complete hand of A. sediba MH2 has a gracile but remarkably long thumb, outside the range of variation in recent humans3. Hand 1 also has a long thumb: the first ray length (Mc1+PP1=61.9 mm) is 58% of the third (Mc3+PP3+IP3=107.5 mm), falling only within the upper range of variation in modern human males (mean 55%) and outside the female range of variation (mean 54%; Fig. 2). The curvatures of the pollical carpometacarpal articulation fall within the modern human range of variation, unlike the more curved facets of extant great apes and some other early hominins13. Unlike most australopiths, Hand 1, as well as six additional Mc1 specimens from five other individuals, demonstrate that H. naledi has markedly robust pollical metacarpals with well-developed crests for the opponens pollicis and the first dorsal interosseous muscles (Fig. 3, Supplementary Fig. 1, Supplementary Table 1 and Supplementary Note 1). The former muscle is functionally important for opposition of the thumb to the fingers, as well as holding and manipulating large objects, whereas the latter muscle is strongly recruited during precision and precision-pinch grips14. In H. naledi, the flaring crests on the Mc1 for the intrinsic thenar muscles are accompanied by a prominent palmar ridge running sagittally along the midshaft (Fig. 3). Overall, the well-developed thenar muscle attachments are most similar to those seen in modern humans, Neandertals, and the Swartkrans pollical metacarpals (SK 84 and SKX 5020, attributed to either A. (Paranthropus) robustus or early Homo)151617. In contrast, they are unlike the weakly developed muscle attachments of gracile australopiths31112 and Ardipithecus ramidus18.

Bottom Line: Based on associated hominin material, the bones of this hand are attributed to Homo naledi.However, the finger bones are longer and more curved than in most australopiths, indicating frequent use of the hand during life for strong grasping during locomotor climbing and suspension.These markedly curved digits in combination with an otherwise human-like wrist and palm indicate a significant degree of climbing, despite the derived nature of many aspects of the hand and other regions of the postcranial skeleton in H. naledi.

View Article: PubMed Central - PubMed

Affiliation: Animal Postcranial Evolution Lab, Skeletal Biology Research Centre, School of Anthropology and Conservation, University of Kent, Marlowe Building, Canterbury CT2 7NR, UK.

ABSTRACT
A nearly complete right hand of an adult hominin was recovered from the Rising Star cave system, South Africa. Based on associated hominin material, the bones of this hand are attributed to Homo naledi. This hand reveals a long, robust thumb and derived wrist morphology that is shared with Neandertals and modern humans, and considered adaptive for intensified manual manipulation. However, the finger bones are longer and more curved than in most australopiths, indicating frequent use of the hand during life for strong grasping during locomotor climbing and suspension. These markedly curved digits in combination with an otherwise human-like wrist and palm indicate a significant degree of climbing, despite the derived nature of many aspects of the hand and other regions of the postcranial skeleton in H. naledi.

No MeSH data available.


Related in: MedlinePlus