introduction conclusions acknowledgments methods

“

Neandertals lacked the pronounced lumbar lordosis present in modern humans (1). Variation in lordosis has implications for lumbopelvic function and the biomechanics of gait. This comparative morphological study of lumbar and pelvic traits in 39 adult humans and three Neandertals evaluates the ways in which hypolordosis

is expressed in both groups.

”

Hominin hypolordosis:

a functional comparison of Neandertal and modern human lumbopelvic anatomy

Maria Fox , Katherine Whitcome 1,2

1

University of Cincinnati 2 University of Illinois at Urbana-Champaign 1

INTRODUCTION ––Neandertals differ from all hominins in their uniquely reduced lumbar lordosis (Figure 1b) (1) ––Strong lordosis evolved millions of years ago with the hominin transition to upright bipedal walking (2-4) ––Lumbar lordosis improved stability and strength during standing and walking (5-9) ––The absence of a marked lordosis in Neandertals is surprising given both the evolutionary and biomechanical relevance of the lumbar curve in bipedal locomotion ––This morphological study compared modern human and Neandertal lumbopelvic anatomy to examine skeletal correlates of lumbar hypolordosis

CONCLUSIONS Hypolordotic traits ––Hypolordotic specimens had more kyphotic wedging angles, ventrocaudally placed, longer transverse processes, and wider sacra but narrower ilia Figure 1. (A) modern human and (B) Neandertal lumbar lordosis. Been et al., 2012.

––These traits combine to create a less mobile, more muscular lumbar region Human lumbopelvic traits ––Sacral shape index (SSI) and iliac breadth (MLB) exhibited differences among lordosis groups

METHODS ––39 modern human males from the CMNH, aged 21-40; 3 male Neandertals ––Linear and angular measurements collected (or calculated) from lumbar vertebrae, sacra, and innominates ––Neandertal measurements gathered from published sources of Kebara 2, La Chapelle-aux-Saints, and Shanidar 3 (1, 4, 10-13) and direct measurements of Kebara 2 innominate

3 4

––Lordosis group determined by wedging at each vertebra

1 2

Figure 2. Sample of vertebral measurements. 1: mediolateral length (ML), 2: anteroposterior length (APL), 3: transverse process length (TPL), 4: TP horizontal angle (TPHA). Gray, 1966.

––Principal components analysis (PCA) confirmed that lordosis groups cluster in multivariate analysis of lumbopelvic traits ––Suggests that wedging angles are one portion of a larger functional lordotic suite Hypolordotic lumbopelvic complex ––Hypolordotic specimens’ wedging angles were significantly more kyphotic in all but L5

––Descriptive statistics examined distributions and normality

––Several transverse process angles differed between hypolordotic humans and Neandertals

––Statistical analyses performed in JMP and R (Wilcoxon Rank Sums tests, linear regression, correlation, PCA) to examine differences between species and lordosis groups

––PCA showed that Neandertals are most similar to hypolordotic humans

RESULTS

––Neandertal lumbopelvic traits are functionally similar to those of hypolordotic humans, though Neandertals may have greater mechanical advantage during lateral flexion (4)

Transverse Processes

9

Horizontal Angle H. sapiens Kebara 2

hypolordotic humans (including 3 Neandertals)

p-values by Species

p-values by Lordosis

23

normal humans

L1 WA

0.01446*

0.02864*

L2 WA

0.03902*

0.00026*

10

hyperlordotic humans

L3 WA

0.00017*

< 0.0001*

L4 WA

0.00923*

0.00033*

L5 WA

0.2966

0.8813

0.01026*

0.00013*

Total WA Kyphotic

Table 1. p-value results for two-sample Wilcoxon Rank Sums tests (comparison by species) and three-sample Kruskal-Wallis tests (comparison by lordosis group) of individual and total wedging angles. Vertebral column from Gray, 1966.

Kebara 2

140

Figure 4. Normal (green) and hypolordotic (blue) modern human transverse process angles and length versus those of Kebara 2 (black). Significant differences (p < 0.05) denoted by an asterisk. Figure adapted from Been et al., 2010.

MAB MLB

170

Iliac Mediolateral Breadth

Sacral Shape Index (SSI)

10

Total Wedging Angle

130

5

120

0

-5

160

Shanidar 3

110 Kebara 2

1. Been E, Gómez-Olivencia A, Kramer PA. 2012. Lumbar lordosis of extinct hominins. Am J Phys Anthropol 147:64–77.

8. Lovejoy CO. 2005. The natural history of human gait and posture. Part 1. Spine and pelvis. Gait & Posture 21:95–112.

2. Robinson JT. 1972. Early hominid posture and locomotion. Chicago: University of Chicago Press.

9. Whitcome KK. 2012. Functional implications of variation in lumbar vertebral count among hominins. J Hum Evol 62:486–497.

3. Sanders WJ. 1995. Function, allometry, and evolution of the australopithecine lower precaudal spine.

10. Trinkaus E. 1982. The Shanidar 3 Neandertal. Am J Phys Anthropol 57:37–60.

5. Davis PR. 1961. Human lower lumbar vertebrae: Some mechanical and osteological considerations. J Anat 95:337–44. 6. Farfan HF. 1978. The Biomechanical Advantage of Lordosis and Hip Extension for Upright Activity: Man as Compared with Other Anthropoids. Spine 3:336–342. 7. Aiello L, Dean C. 1990. The Hominoid Thorax and Vertebral Column. In: An Introduction to Human Evolutionary Anatomy. San Diego: Academic Press. p 275–308.

VH

Shanidar 3

BIBLIOGRAPHY

4. Been E, Peleg S, Marom A, Barash A. 2010. Morphology and function of the lumbar spine of the Kebara 2 Neandertal. Am J Phys Anthropol 142:549–57.

Lordotic

Figure 3. Vertebral wedging angle (WA) as calculated in this study. From Bonmatí et al., 2010.

15

Coronal Angle H. sapiens Kebara 2

11. Arensburg B. 1991. The Vertebral Column, Thoracic Cage and Hyoid Bone. In: Le squelette moustérien de Kébara 2. Paris: Editions du C.N.R.S. p 125–146. 12. Rak Y. 1991. The Pelvis. In: Le squelette moustérien de Kébara 2. Paris: Editions du C.N.R.S. p 147–156. 13. Bonmatí A, Gómez-Olivencia A, Arsuagaa J-L, Carretero JM, Gracia A, Martínez I, Lorenzo C, Castro JMB de, Carbonell E. 2010. Middle Pleistocene lower back and pelvis from an aged human individual from the Sima de los Huesos site, Spain. PNAS 107:18386–18391.

IMAGE CREDITS Cheselden W. 1733. Osteographia, of The anatomy of the bones. London: William Bowyer. (image directly to left) Gray H. 1966. Gray’s Anatomy. 28th ed. (Goss CM, editor.). Philadelphia: Lea & Febiger.

Kebara 2

150

-10

100

hypolordotic

normal

hyperlordotic

hypolordotic

Figure 5. Total (summed) wedging angle by lordosis group. Neandertal points added as triangles. Lordosis groups significantly different at p=0.00013. Individual wedging angle differences reported in Table 1.

4

hypolordotic normal hyperlordotic

2

28

3 42 39

5 hypolordotic

16

40

4 17 8 20 33 7 27 13 normal 32 41 23 35 18 9 38 31 15 hyperlordotic 36 26 19 30 1 37 21 34 25 11

0

6

-2

Dim 2 (17.41%)

22

10

14

29

24

-2

0

2

4

Dim 1 (23.19%)

Figure 8. PCA of human and Neandertal lumbopelvic variables (detailed in Table 2) with 95% confidence ellipses (Neandertal-only confidence ellipse in blue).

hypolordotic

normal

hyperlordotic

Figure 7. Iliac mediolateral breadth (MLB) by lordosis group (p=0.2865). Neandertal points added as triangles.

ACKNOWLEDGMENTS Funding: The Charles Phelps Taft Research Center at the University of Cincinnati. Department of Anthropology, University of Illinois at Urbana-Champaign.

Variable

Dim 1

Ctr

Dim 2

Ctr

Vertebrae L1 WA

0.334

3.444

0.428

7.512

L2 WA

0.610

11.463

0.354

5.149

L3 WA

0.551

9.352

0.507

10.547

L4 WA

0.463

6.608

0.216

1.909

L5 WA

-0.350

3.780

0.007

0.002

Sacrum MAB (Max Anterior Breadth)

0.607

11.359

0.059

0.142

VH (Ventral Height)

0.660

13.781

-0.661

17.943

MSB (Middle Sacral Breadth)

0.718

15.879

0.221

2.005

CMLL (Centrum Mediolateral Length)

0.313

3.018

0.516

10.906

CAPL (Centrum Anteroposterior Length)

0.129

0.511

0.322

4.253

-0.322

3.203

0.746

22.852

Pelvis CCL (Craniocaudal Length)

0.443

6.047

-0.228

2.126

MLB (Mediolateral Breadth)

0.302

2.809

-0.128

0.668

SO (Sacropelvic Orientation)

-0.533

8.746

0.584

13.985

SSI (Sacral Shape Index)

-4

12

-4

hyperlordotic

Figure 6. Sacral shape index (SSI = (MAB/VH)*100) by lordosis group (p=0.0585). Larger values indicate a wide, short sacrum. Neandertal points added as triangles.

Confidence ellipses around the categories of Lordosis

2

normal

Table 2. PCA dimension 1 and 2 coordinates and contributions for selected lumbopelvic variables.

Support: Dr. Brooke Crowley, Dr. Heather Norton, Dr. John Polk, Dr. Laura Shackelford Thanks to Lyman Jellema and the Cleveland Museum of Natural History (CMNH) for granting access to their collections.