The evolution of Homo neanderthalensis to Homo sapiens

1. The evolution of Homo neanderthalensis to Homo sapiens Alex Noble Bradley Weiss Brittany Wike

2. Anatomy differences between the two species

3. Questions to be answered: braincase • Could a lower braincase with higher bone density of Homo neanderthalensis give them an advantage in protection from head trauma?

4. Brain case: frontal view

5. Brain case: side view

6. Brain case: back view

7. Brain case Image G shows Guattari, or a “classic” Homo neanderthalensis skull. Image H shows Homo sapiens

8. Bone density Left: Thick walled bones are characteristic of Homo neanderthalensis; indicating a higher bone density. Right: Thin walled bones are characteristic of Homo sapiens; indicating less bone density.

9. Questions to be answered: bone density • Were Homo neanderthalensis exposed to more traumatic environments?

10. Bone Density Percentage distributions of traumatic lesions by anatomical region for Neanderthals without DJD vs. Recent human clinical samples

11. Bone Density Figure shows the combined cortical thickness of the humerus; anteroposterior and mediolateral views of Homo neanderthals, early Homo sapiens, and modern Homo sapiens.

12. Mandible • Homo neanderthalensisskull and mandible from the Smithsonian

13. Why the Mandible? • In modern H. sapiens, the ascending mandibular ramus are in two processes, the coronoid and condylar process, and separated by a deep notch. • In Neanderthals, the coronoid appears larger and more elevated than the condylar process, with a shallow notch in between.

14. Methods • Traced the mandibular notch of each specimen. • While using the Condylar and Coronoid Processes as fixed points.

15. Mandibular Tracing • Outline of mandibular notch in the Neanderthal, top arrow. • Mean outline of 250 modern human specimens, bottom arrow.

16. Discussion • Mandibular ramus is a truly diagnostic character for Neanderthals. • Analysis shows Neanderthals face and braincase clearly indicate the species’ unique taxonomic status.

17. Rak et al concluded that based on the mandibular ramus, Homo neanderthalensis forms a side branch that evolved differently from the modern human. Led to the conclusion that Neanderthals do not play a role in our biological ancestry.

18. Thoracic Cavity • Neanderthals have a longer and wider sternum • Longer and curved clavicles giving them a deeper and wider chest

19. Case Study • Weinstein: used results found by other researchers • 2 Neanderthals, 2 early modern humans, and 4 human skeletons from the Andes. • Comparing the thorax of human fossils to Neanderthals • Also to see if higher altitudes made a difference

20. Significance of the hyper-barrel-shaped thorax of the Neanderthal Two main factors: • Enhanced respiratory volume and aerobic capacities that function as adaptations to elevated activity levels • Adaptations to cold climates

21. Comparisons to the Andes • Rib length and respiratory area are larger in the Neanderthal sample than the human fossils found in the Andes • Early human fossils had reduced rib measurements and a narrower thoracic cavity

22. Data R8TVC, R8TVS, LR8RAHUM

23. Results • The large thorax was an advantage to both factors • Large thorax reduced surface area to body mass, which reduces body heat lost to the environment • Large thorax also allowed for great lung capacity and ventilation which was needed for high physical activity and high metabolic rates

24. Difficulties in the Study? • Finding full or near full ribcages to do studies on • Low sample sizes • More data will allow for a better understanding

25. Daily Energy Requirements • Sorenson and Leonard • Estimated their total energy expenditure by calculating their basal metabolic rates • Neanderthals ranged from 3000-5500 kcal/day • Modern human populations ranged from 2720 +/- 607 kcal/day • Neanderthals had higher energy requirements daily

26. Future Research • Comparing the thickness of the braincase for both species. The head trauma that H. neanderthalensis’ displayed may increase the density of the skull. • Comparing rib measurements: including lengths, cross sections, muscle rigidity, and degree of curvature

27. Works Cited • Howells W. (1975) Neanderthal man: facts and figures. Paleoanthropology: morphology and paleoecology. Paris: Mouton. 389–407. • Rak, Y. et al. (2002) Does Homo neanderthalensis Play a Role in Modern Human Ancestry? The Mandibular Evidence. Am J Phys Anthropol 119:199-204. • Humphrey, L.T., M.C. Dean, C.B. Stringer. (1999) Morphological variation in great ape and modern human mandibles. J. Anat. 195:491-513. • Itzhak-Ben, S., Smith, P., Bloom, R.A. (1988) Radiographic Study of the Humerus in Neanderthals and Homo sapiens sapiens. American Journal of Physical Anthropology. 77: 231-242. • Berger, T.D., Trinkaus, E. (1995) Patterns of Trauma among the Neanderthals. Journal of Archaeological Science. 22: 841-852. • Bookstein, F., Schafer, K., Prossinger, H., Seidler, H., Fieder, M., Stringer, C., Weber, G.W., Arsuaga, J.L., Slice, D.E., Rohlf, F.J., Recheis, W., Mariam, A,J., Marcus, L.F. (1999) Comparing Frontal Cranial Profiles in Archaic and Modern Homo by Morphometric Analysis. The Anatomical Record (New Anat.) 257: 217-224. • Folger, T. (1997) Strong Bones, and Thus Dim-witted? Discover Magazine. • Denning, K. (2006, November 6). Humanity’s Journeys. Retrieved April 2011 from http://www.yorku.ca/kdenning/++2140%202006-7/2140-21Nov2006.htm • Weinstein, K. (2008) Thoracic morphology in Near Eastern Neandertals and early modern humans compared with recent modern humans from high and low altitudes. Journal of Human Evolution. 54: 287-295