Biomedical subjects

E Trinkaus

Publications and source records attributed to E Trinkaus.

At least 37 records · Page 2Linked to original sources

PubMed1998

Patterns of sexual, bilateral and interpopulational variation in human femoral neck-shaft angles.

Data on femoral neck-shaft angles were collected for 30 modern, historic and prehistoric human population samples, and analysed with respect to sexual dimorphism, bilateral asymmetry, geographical patterning and general economic level. Although some samples had modest sexual dimorphism in this angle, and some individuals exhibited clear asymmetry, there were no consistent patterns of sexual or side differences across human populations. Similarly, there was no evidence for geographic differences, since broad regional groups lacked significant differences and mean angles were not correlated with latitude. However, there is a significant increase in mean neck-shaft angles across populations with an increasingly sedentary existence and with mechanisation. The last reflects the developmental plasticity of this feature with respect to habitual load levels during ontogeny of the hip region.

Africa South of the Sahara↗

PubMed1997

Appendicular robusticity and the paleobiology of modern human emergence.

The emergence of modern humans in the Late Pleistocene, whatever its phylogenetic history, was characterized by a series of behaviorally important shifts reflected in aspects of human hard tissue biology and the archeological record. To elucidate these shifts further, diaphyseal cross-sectional morphology was analyzed by using cross-sectional areas and second moments of area of the mid-distal humerus and midshaft femur. The humeral diaphysis indicates a gradual reduction in habitual load levels from Eurasian late archaic, to Early Upper Paleolithic early modern, to Middle Upper Paleolithic early modern hominids, with the Levantine Middle Paleolithic early modern humans being a gracile anomalous outlier. The femoral diaphysis, once variation in ecogeographically patterned body proportions is taken into account, indicates no changes across the pre-30,000 years B.P. samples in habitual locomotor load levels, followed by a modest decrease through the Middle Upper Paleolithic.

Biological Evolution↗

PubMed1997

Body mass and encephalization in Pleistocene Homo.

Many dramatic changes in morphology within the genus Homo have occurred over the past 2 million years or more, including large increases in absolute brain size and decreases in postcanine dental size and skeletal robusticity. Body mass, as the 'size' variable against which other morphological features are usually judged, has been important for assessing these changes. Yet past body mass estimates for Pleistocene Homo have varied greatly, sometimes by as much as 50% for the same individuals. Here we show that two independent methods of body-mass estimation yield concordant results when applied to Pleistocene Homo specimens. On the basis of an analysis of 163 individuals, body mass in Pleistocene Homo averaged significantly (about 10%) larger than a representative sample of living humans. Relative to body mass, brain mass in late archaic H. sapiens (Neanderthals) was slightly smaller than in early 'anatomically modern' humans, but the major increase in encephalization within Homo occurred earlier during the Middle Pleistocene (600-150 thousand years before present (kyr BP)), preceded by a long period of stasis extending through the Early Pleistocene (1,800 kyr BP).

Animals↗

PubMed1997

Neandertal capitate-metacarpal articular morphology.

Neandertal capitate-metacarpal 2 and 3 articulations have been observed to differ in orientation and shape from those of more recent humans. To evaluate this, we tested for differences in capitate-metacarpal 2 (MC2) and MC2-capitate facet orientations and MC2 and MC3 robusticity indices, and for multivariate shape equivalence of the capitate-MC2/MC3 facets and the MC3 diaphysis and styloid process between samples of Neandertals and recent humans. Canonical discriminant functions of log size- and-shape and log shape transformed measurements were run on variables of the capitate-MC2 and MC3 facets, and these plus MC3 diaphysis and styloid process variables. The null hypothesis of shape equivalence is rejected for both variable sets. Modern human capitate-MC morphology results from nonallometric increases in distal capitate breadth and the projection of the MC3 styloid process, and reductions in MC2 facet height and MC3 facet breadth. These shape changes are associated with a significantly less parasagittal orientation of the capitate-MC2 facets in recent humans, but are only trivially correlated with MC 2 and 3 robusticity indices. The recent human capitate-MC 2 and 3 morphology may reflect a shift in habitual joint reaction forces from more axial to more oblique forces while maintaining similar pronation/supination of the MC2. However, the full behavioral implications of these contrasts remain unclear.

Animals↗

PubMed1997

Neandertal incisor beveling.

In discussions of the Neandertals, there has been repeated emphasis on the accelerated rate of attrition and the frequent presence of labial beveling of their incisors. Interpretations of this dental attrition have related it to paramasticatory and dietary uses of their anterior teeth as well as to aspects of their facial morphology. In light of this, we examined the rate of beveling (the angle between the labial and incisal surfaces) of central incisors relative to tooth wear in samples of Neandertals, Inuits and Puebloan Amerindians. I1s show little change in the beveling angle with wear and no significant differences between the samples. I1s, however, exhibit a consistent pattern of increased beveling with dental attrition, progressing rapidly until the crown height approximates its labiolinguinal cervical diameter, and then proceeding at a slower rate. All three samples exhibit a similar pattern. However, the Neandertals have significantly greater beveling in more worn teeth than either recent human sample, and the Inuits have nonsignificantly increased beveling relative to the Puebloans in these more worn I1s. In this, it is the degree of development of beveling, not the pattern of beveling, which differentiates the Neandertals. It is hypothesized that the differences between the Neandertals and recent samples could be the product of: (1) contrast in initial incisor procumbency, (2) a labial separation of the maxillary and mandibular incisal occlusal surfaces during edge-to-edge bite, and/or (3) a greater degree of interproximal wear promoting increased "posterior tipping" of the maxillary incisors. The last appears most likely.

Animals↗

PubMed1997

Human remains from the Moravian Gravettian: the Dolní Vĕstonice 3 postcrania.

To add to our knowledge of European earlier Upper Paleolithic (especially Pavlovian) human biology, the postcranial skeleton of the Dolní Vĕstonic 3 partial skeleton was excavated and reassembled. It represents the remains of an adult female, who was buried in a tightly flexed position with the ventral side down and turned slightly to the left. Subsequent compaction led to extensive damage to the axial skeleton and long bone epiphyses. It nonetheless retains the C1 and C2, fragments of the C5 to S3, portions of the pelvis, most of the long bone diaphyses, and a number of manual and pedal remains. Dolní Vĕstonice 3 was a relatively gracile individual in terms of diaphyseal robusticity and especially muscular attachment rugosity, despite the strong development of femoral and tibial diaphyseal structural buttresses. Upper limb asymmetry is slight and variable. She is similar to other earlier Upper Paleolithic remains in having warm temperate to tropical body proportions but is at the lower limit of Gravettian variation in body size indicators. There is no evidence of significant antemortem lesions on the preserved postcrania.

Adult↗

PubMed1997

A reconsideration of the Archi 1 Neandertal mandible.

A reassessment of the early last glacial immature Neandertal mandibular corpus from Archi indicates a series of features in which it closely resembles other pre-adolescent Neandertal mandibles and contrasts with those of similarly aged recent humans. These are in the context of a re-aging of the specimen to ca. 3 years on the basis of deciduous dental eruption and attrition and permanent dental calcification. The Archi 1 mandible resembles other immature. Neandertals in having a "retreating" symphyseal profile in the context of moderate development of mental trigone features. It is relatively robust in the development of lateral and basilar corpus features and some increased symphyseal and lateral corpus thickness. And it exhibits, along with other Middle Paleolithic immature mandibles, anteriorly wide dental arcades, probably due to large developing anterior permanent tooth crowns.

Age Factors↗

PubMed1996

Dynamic bone remodeling in later Pleistocene fossil hominids.

Histomorphometric analysis of femoral and tibial diaphyseal fragments from seven Late Archaic and three Early Modern humans are compared with those of the Pecos, a pre-Columbian Native American population. The ten samples, from Broken Hill (EM-793), Shanidar 2, 3, 4, 5, and 6, Tabun 1, and Skhul 3, 6, and 7, provide age-at death results consistent with earlier estimates for most individuals. The Pleistocene groups exhibit less bone turnover and smaller osteons than Recent populations. Resorption and formation were both coupled and balanced in these Pleistocene populations, but the overall vigor of individual cells from both the osteoclast and osteoblast cell lines was less than in Recent populations. Thus the greater bone mass in Later Pleistocene members of the genus Homo is not the result of higher levels of bone turnover, at least among adults.

Age Determination by Skeleton↗

PubMed1996

The M. obturator internus sulcus on middle and late Pleistocene human ischia.

Recent human ischia and those of Middle and Late Pleistocene hominids exhibit variation in the cranio-caudal location of the sulcus for the internal obturator muscle as it rounds the ischium through the lesser sciatic notch, from being fully cranial of the ischial tuberosity, to bordering the tuberosity, to crossing the superior tuberosity. Among two recent human samples, all three forms exist, with the cranial position of the sulcus being more common in a 20th century Euroamerican sample whereas the intermediate one predominates in a horticultural late prehistoric Amerindian sample. The available Pleistocene Homo fossil remains exhibit the full range of variation with no one form being dominant in Middle Pleistocene archaic humans and Middle Paleolithic late archaic and early modern humans. It is only within the Upper Paleolithic that the cranial and intermediate locations for the sulcus become predominant. These patterns therefore indicate that it is inappropriate to use this feature for distinguishing later Pleistocene hominid groups.

Animals↗

PubMed1994

Postcranial robusticity in Homo. II: Humeral bilateral asymmetry and bone plasticity.

The analysis of humeral asymmetry in Recent human skeletal samples and an extant tennis-player sample documents minimal asymmetry in bone length, little asymmetry in distal humeral articular breadth, but pronounced and variable asymmetry in mid- and distal diaphyseal cross-sectional geometric parameters. More specifically, skeletal samples of normal modern Euroamericans, prehistoric and early historic Amerindians, and prehistoric Japanese show moderate (ca. 5-14%) median asymmetry in diaphyseal cross-sectional areas and polar second moments of area, whereas the tennis-player sample, with pronounced unilateral physical activity, exhibits median asymmetries of 28-57% in the same parameters. A sample of Neandertals with nonpathological upper limbs exhibits similarly low articular asymmetry but pronounced diaphyseal asymmetries, averaging 24-57%. In addition, three Neandertals with actual or possible post-traumatic upper limb alterations have the same low articular asymmetry but extremely high diaphyseal asymmetries, averaging 112-215%. These data support those from experimental work on animals, exercise programs of humans, and human clinical contexts in establishing the high degree of diaphyseal plasticity possible for humans, past and present, under changing biomechanical loading conditions. This lends support to activity-related functional interpretations of changing human diaphyseal morphology and robusticity during the Pleistocene.

Animals↗

PubMed1994

Postcranial robusticity in Homo. III: Ontogeny.

The influence of developmental factors on long-bone cross-sectional geometry and articular size in modern humans is investigated using two approaches: (1) an analysis of the effects of increased mechanical loading on long-bone structure when applied during different developmental periods, using data collected for a study of upper limb bone bilateral asymmetry in professional tennis players; and (2) an analysis of the relative timing of age changes in femoral dimensions among juveniles from the Pecos Pueblo Amerindian archaeological sample. Results of these analyses are used to interpret the femoral morphology of three pre-Recent Homo juveniles--the H. erectus KNM-WT 15000 and the archaic H. sapiens La Ferrassie 6 and Teshik-Tash 1--as well as observed differences in postcranial morphology between adult Recent and earlier Homo (Ruff et al., 1993). Our findings indicate the following: (1) There are age-related changes in long-bone diaphyseal envelope sensitivity to increased mechanical loading, with the periosteal envelope more responsive prior to mid-adolescence, and the endosteal envelope more responsive thereafter. The periosteal expansion and endosteal contraction of the diaphysis documented earlier for adult pre-Recent Homo relative to Recent humans (Ruff et al., 1993) is thus consistent with a developmental response to increased mechanical loading applied throughout life. The relatively large medullary cavity in the 11-12-year-old KNM-WT 15000 femur is also consistent with this model. However, the two archaic H. sapiens juveniles show relatively small medullary cavities, possibly indicating a modified developmental pattern in this group. (2) Articulations follow a growth pattern similar to that of long-bone length (and stature), while cross-sectional diaphyseal dimensions (cortical area, second moments of area) show a contrasting growth pattern, with slower initial growth from childhood through mid-adolescence, followed by a "catch-up" period that continues through early adulthood. This latter pattern is more similar to the growth curve for body weight, and may in fact partially reflect adaptation of the diaphysis to increased weight bearing. Because of these different growth patterns, articulations appear relatively large, and diaphyseal breadths relatively small during late childhood to mid-adolescence (i.e., about 9-13 years), when compared to adults from the same population. KNM-WT 15000 shows this same proportional difference from adult early Homo specimens, which is therefore interpreted as simply a developmental consequence of his age at death.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗

PubMed1994

Early ontogeny of the human femoral bicondylar angle.

The presence of a femoral bicondylar angle consistently and significantly greater than 0 degrees has been a hallmark of hominid bipedality, but its pattern of development has not been documented. We have therefore compiled cross-sectional data on the development of the articular bicondylar angle for a clinical sample of modern humans and of the metaphyseal bicondylar angle for two Recent human skeletal samples, one predominantly European in origin and the other Amerindian. All three samples exhibit a pattern of a bicondylar angle of 0 degrees at birth and then a steady average increase in the angle from late in the first year postnatal, through infancy; and into the juvenile years. The two skeletal samples reach low adult values by approximately 4 years postnatal, whereas the clinical sample with a lowered activity level appears to attain consistent adult values slightly later (approximately 6 years postnatal). In addition, two modern human individuals, one nonambulatory and the other minimally ambulatory, show no and little development, respectively, of a bicondylar angle. These data, in conjunction with clinical and experimental observations on the potential and form of angular changes during epiphyseal growth, establish a high degree of potential for plasticity in the development of the human bicondylar angle and the direct association of a bipedal locomotion and (especially) posture with the developmental emergence of a human femoral bicondylar angle.

Adolescent↗

PubMed1993

Postcranial robusticity in Homo. I: Temporal trends and mechanical interpretation.

Temporal trends in postcranial robusticity within the genus Homo are explored by comparing cross-sectional diaphyseal and articular properties of the femur, and to a more limited extent, the humerus, in samples of Recent and earlier Homo. Using both theoretical mechanical models and empirical observations within Recent humans, scaling relationships between structural properties and bone length are developed. The influence of body shape on these relationships is considered. These scaling factors are then used to standardize structural properties for comparisons with pre-Recent Homo (Homo sp. and H. erectus, archaic H. sapiens, and early modern H. sapiens). Results of the comparisons lead to the following conclusions: 1) There has been a consistent, exponentially increasing decline in diaphyseal robusticity within Homo that has continued from the early Pleistocene through living humans. Early modern H. sapiens are closer in shaft robusticity to archaic H. sapiens than they are to Recent humans. The increase in diaphyseal robusticity in earlier Homo is a result of both medullary contraction and periosteal expansion relative to Recent humans. 2) There has been no similar temporal decline in articular robusticity within Homo--relative femoral head size is similar in all groups and time periods. Thus, articular to shaft proportions are different in pre-Recent and Recent Homo. 3) These findings are most consistent with a mechanical explanation (declining mechanical loading of the postcranium), that acted primarily through developmental rather than genetic means. The environmental (behavioral) factors that brought about the decline in postcranial robusticity in Homo are ultimately linked to increases in brain size and cultural-technological advances, although changes in robusticity lag behind changes in cognitive capabilities.

Animals↗

PubMed1992

Shanidar 1: a case of hyperostotic disease (DISH) in the middle Paleolithic.

The Shanidar 1 Neandertal partial skeleton presents osteophytic lesions on its vertebrae and appendicular skeleton which appear independent of the multiple traumatic and degenerative joint disease lesions on the individual. In particular, the large flowing osteophyte on the L3 body, a smaller one on the L5 body, and enthesopathic osteophytes on both calcaneal tuberosities, both patellae and the left ulnar olecranon, support a diagnosis of hyperostotic disease (DISH). The diagnosis is supported by small enthesopathic osteophytes on the preserved femoral greater trochanter and scapular corocoid process. This diagnosis would make it the oldest hominid specimen clearly presenting this systemic condition.

Animals↗

PubMed1991

Mechanical advantages of the Neanderthal thumb in flexion: a test of an hypothesis.

It has been proposed that the pollical phalangeal length proportions of the Neanderthals provided them with a greater mechanical advantage relative to recent humans for their pollical flexor muscles in power grips across the interphalangeal (IP) joint at the expense of the mechanical advantage of those pollical flexor muscles in precision grips at the finger tip. To test these related hypotheses, we compared the pollical load arm dimensions (phalanx lengths) to power arm dimensions (dorsopalmar articular heights) for the European and Near Eastern Neanderthals and for European and Amerindian samples of recent humans. It was found, initially, that the proximal articular height of the pollical distal phalanx is a poor predictor of the power arm at the IP articulation, even though the proximal articular height of the pollical proximal phalanx was an adequate indicator of the power arm size at the metacarpophalangeal (MCP) joint. In addition, differences in distal pollical ulnar deviation at the IP joint appeared to make little difference in the mechanical advantage comparisons. More importantly, the relative shortness of Neanderthal proximal pollical phalanges and the relative lengthening of their distal pollical phalanges was confirmed, and it was determined that, despite some minor differences in articular dimensions between Neanderthals and recent humans, these pollical phalangeal length contrasts translated into significant differences in mechanical advantages for the flexor muscles across the MCP and IP articulations.

Animals↗

PubMed1990

Cladistics and the hominid fossil record.

Cladistic methodology has become common in phylogenetic analyses of the hominid fossil record. Even though it has correctly placed emphasis on morphology for the primary determination of affinities between groups and on explicit statements regarding traits and methods employed in making phylogenetic assessments, cladistics nonetheless has limitations when applied to the hominid fossil record. These include 1) the uncritical assumption of parsimony, 2) uncertainties in the identification of homoplasies, 3) difficulties in the appropriate delimitation of samples for analysis, 4) failure to account for normal patterns of variation, 5) methodological problems with the appropriate identification of morphological traits involving issues of biological relevance, intercorrelation, primary versus secondary characters, and the use of continuous variables, 6) issues of polarity identification, and 7) problems in hypothesis testing. While cladistics has focused attention on alternative phylogenetic reconstructions in hominid paleontology and on explicit statements regarding their morphological and methodological underpinnings, its biological limitations are too abundant for it to be more than a heuristic device for the preliminary ordering of complex human paleontological and neonatological data.

Animals↗

PubMed1990

Neandertal scapular glenoid morphology.

Analysis of Neandertal and recent human scapular glenoid fossae reveals that the former had long, narrow, and flat glenoid articular surfaces relative to those of modern humans. Comparison of glenoid length, breadth, and curvature to humeral articular dimensions demonstrates that Neandertal glenoid length and curvature scale to proximal and distal humeral articular dimensions in the same manner as those of modern humans. The remaining contrast is in the relatively greater glenoid fossa width seen in modern humans. This difference in morphology implies differences in the habitual degree of dorsoventral glenohumeral movement between Neandertals and modern humans. This in turn may be related to contrasts in tool use, especially with respect to throwing and projectile use.

Animals↗

PubMed1990

Species attribution of the Swartkrans member 1 first metacarpals: SK84 and SKX 5020.

Susman (Am. J. Phys. Anthropol. 75:277-278, 79:451-474; Science 240:781-784; In FE Grine (ed): Evolutionary History of the "Robust" Australopithecines. New York: Aldine de Gruyter, pp. 149-172) has attributed the morphologically similar SK 84 and SKX 5020 hominid first metacarpals to Homo erectus and Australopithecus robustus, respectively, and has inferred that both species exhibited derived pollical morphologies, indicating refined precision grips. Consideration of the structure of his taphonomic arguments indicates that there are no adequate nonmorphological reasons to attribute these specimens securely to one or the other of the craniodentally represented species at Swartkrans. His morphological arguments fail to note any significant differences between the two specimens. Only the contrast in size between the small SK 84 and large SKX 5020 bones might warrant a species distinction; yet comparison of their length ratio to distributions of modern human first metacarpal length ratios indicates that it is not possible to reject conclusively the null hypothesis that they are conspecific. Therefore, early hominid adaptive scenarios based on a derived Homo-like manual functional morphology in A. robustus remain without a secure paleontological basis.

Animals↗