3D geometric morphometrics of Microcephalic and Cretin mandibles support the new species diagnosis of

LB1 (Homo floresiensis)

1Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University, 2Department of Anatomical Sciences, Stony Brook University Medical Center

Kyle Marian A Viterbo1, William Jungers2

The Hobbit of Flores, Indonesia

Brown et al. 2004; Brown and Maeda 2009; Morwood et al. 2005; map – Voris 2004

The Hobbit of Flores, IndonesiaCompeting Hypotheses

1) Remnant of a pre-H. erectus or early Homo dispersal out of Africa

2) Island-dwarfed Asian Homo erectus

3) Modern human from Asian Pygmy population

4) Small-bodied pathological modern human

Argue et al. 2006; Baab and McNulty 2008; Baab et al. 2007; Bromham and Cardillo 2007; Brown et al. 2004; Hershkovitz and Kornreich 2007; Jacob et al. 2006; Kaifu et al. 2011

Sangiran 17 (left) and LB1 (right).

The Hobbit of Flores, Indonesia

Unusual modern Homo sapiens? Recent dates = recent modern population? Modern dwarfed Australomelanesian Pygmy skeleton (Jacob et al. 2006)

Negative/neutral “chin” also found in Australomelanesian populations Short stature not unusual for Island Southeast Asia

Small-cranium pathology (Microcephaly, Cretinism, Laron Syndrome, etc.)

Do the LB1 and LB6 mandibles fall within the range of anatomically modern human shape variation?

X-ray & profile of a male Rampasasa Pygmy from Flores (Jacob et al. 2006)

Microcephaly Cretinism (Hypothyroidism)

Mandibles in Paleoanthropology

Mandibles represent a large portion of the Human fossil record.

Mandibular morphology• Recognizing new species• Designating taxonomy to

fossil finds

Ardipithecus ramidus

Australopithecus anamensis

Praeanthropus afarensis

A. bahrelghazali

Homo antecessor

Bermúdez de Castro et al. 1997; Kaifu et al. 2005a; Kaifu et al. 2005b; Lague et al. 2008; Nicholson and Harvati 2006; Rosas and Bermúdez de Castro 1998

The Liang Bua Mandibles

DIAGNOSTIC FEATURES① Coronoid process higher

than mandibular condyle

② Posteriorly-oriented ascending ramus

③ No chin

④ Posteriorly-inclined symphyseal axis and alveolar planum

⑤ Presence of an inferior and superior transverse tori

• LB1 and LB6 exhibit the same morphology

• Combines features from Plio-Pleistocene hominins

• Unlike Zhoukoudian and Sangiran H. erectus

Brown et al. 2004; Brown and Maeda 2009

The Liang Bua Mandibles

BROWN & MAEDA (2009)

Compared to Homo sapiens Homo erectus Australopithecus afarensis

Results H. floresiensis outside human

range of variation Shares aspects of symphyseal

and corpus shape, and robusticity with A. afarensis

Molar size, facial height, and corpus shape diverge from australopithecine pattern

a. Homo sapiens from Upper Cave Zhoukoudian, China; b. a microcephalic H. sapiens from Mauritius (Peabody Museum, Harvard Univ.); c. Homo floresiensis (LB1); d. H. floresiensis (LB6); e. early African Homo erectus (KNM-WT 15000); f, Australopithecus afarensis (Laetoli Hominid 4)

MethodsData acquisition• Microscribe G2X digitizer• Landmark.exe

Shape and statistical analysis• Semi-landmarks resampled with

Resample.exe (NYCEP)• Generalized Procrustes Alignment

(GPA)• Principal Components Analysis (PCA) • MANOVA and Canonical Discriminant

Analysis (CDA) • LB1 treated as an unknown

Analysis A: whole mandible78 homologous landmarks

Analysis B: superior ramus omitted66 homologous landmarks

Materials• 250 Non-pathological modern

humans • Adult• Sub-adult• Fossil Homo sapiens• African & Asian Pygmies

• 11 Microcephalic*• Musee de l’Homme• Basel Natural History Museum• Royal College of Surgeons,

Edinburgh

• 18 Cretin (Hypothyroidism)*• Basel Natural History Museum• Royal College of Surgeons,

Edinburgh

• LB1

• Analysis A: 9 Fossil casts and reconstructions

• Analysis B : 18 fossil hominin casts/reconstructions**• Teshik Tash (subadult H. neanderthalensis)

• Pech De l’Aze (subadult H. neanderthalensis)

• Gibraltar 1 (H. neanderthalensis)

• Mauer (H. heidelbergensis)

• La Quina 5 (H. neanderthalensis)

• Lantian 1 (H. erectus)

• Tighenif 3 (H. erectus)

• Amud 1 (H. neanderthalensis)

• Sima de los Huesos 5 (H. heidelbergensis)

• Ehringsdorf Cave (H. sp.)

• Peninj 1 (P. boisei)

• D2735 (Dmanisi H. erectus/ergaster/georgicus)

• DNH7 (Drimolen P. robustus)

• Atlanthropus (H. erectus)

• KNM-WT 15000 (H. erectus/ergaster)

• SK 15 (H. sp.)

• AL 288-1 (A. afarensis)

• MK4 (A. africanus)*Specimens directly correspond with material from Obendorf et al. 2008, Oxnard et al. 2010, Oxnard et al. 2012

RESULTS (A): Principal Components Analysis

PC 1 (20.32%) PC 2 (11.49%) PC 3 (10.79%)

RESULTS (A): Canonical Discrimant Analysis

RESULTS (A): Canonical Discrimant Analysis

CLASSIFICATION RESULTSPredicted Group Membership

Original (%)

Grouping 1 2 3 4Non-Pathological (1) 99.2 0.4 0.4 0.0Microcephalic (2) 18.2 63.6 18.2 0.0Cretin (3) 16.7 5.6 77.8 0.0Fossil Hominin (4) 22.2 0.0 11.1 66.7LB1 (unknown) 0.0 0.0 0.0 100.0

Predicted Group Membership

Cross- validated (%)

Grouping 1 2 3 4Non-Pathological (1) 98.8 0.8 0.4 0.0Microcephalic (2) 45.5 27.3 27.3 0.0Cretin (3) 16.7 27.8 55.6 0.0Fossil Hominin (4) 22.2 0.0 11.1 66.7

RESULTS (B): Principal Components Analysis

PC1 (21.45%) Wireframes

PC2 (13.88%) Wireframes

PC3 (10.46%) Wireframes

RESULTS (B): Canonical Discrimant Analysis

RESULTS (B): Canonical Discrimant Analysis

RESULTS (B): Canonical Discrimant Analysis

Specimen Actual Group

Highest Group Second Highest Group

Predicted Probability Mahalanobis D2 Predicted Probability Mahalanobis D2 MNHN 25298 2 1 81.0% 4.350 2 17.0% 0.521 MNHN 25301* 2 1 74.5% 7.757 2 21.6% 3.280 MNHN 29406 2 1 83.0% 4.969 3 12.0% 1.252 MNHN 30212 2 1 90.0% 5.202 2 9.0% 2.788 MNHN sn 2 1 92.0% 3.557 3 6.0% 1.520 NMB cast 2 1 85.0% 5.014 2 14.0% 1.656 NMB G64 3 1 50.0% 11.265 3 48.7% 3.804 NMB G66 3 1 83.0% 3.608 2 13.5% 0.284 NMB G68 3 1 97.0% 1.017 2 2.0% 1.894 NMB 578 3 2 53.0% 1.195 3 28.0% 1.864 Teshik Tash* (H. neanderthalensis) 4 1 72.4% 9.923 3 23.5% 4.640 Pech de l'Aze* (H. neanderthalensis) 4 3 62.0% 10.271 1 37.0% 18.850 Amud 1 (H. neanderthalensis) 4 1 99.7% 6.772 4 0.3% 13.464 Dmanisi D2735* (H. erectus) 4 1 50.0% 8.381 4 50.0% 3.285 LB1 (unknown) ungrouped 4 98.8% 3.732 1 1.2% 17.718

CLASSIFICATION RESULTSPredicted Group Membership

Original (%)

Grouping 1 2 3 4Non-Pathological (1) 99.6 0.0 0.0 0.4Microcephalic (2) 75.0 25.0 0.0 0.0Cretin (3) 0.05 16.7 77.8 0.0Fossil Hominin (4) 15.0 0.0 5.0 80.0LB1 (unknown) 0.0 0.0 0.0 100.0

Predicted Group Membership

Cross- validated (%)

Grouping 1 2 3 4Non-Pathological (1) 99.2 0.0 0.4 0.4Microcephalic (2) 87.5 0.0 12.5 0.0Cretin (3) 0.05 22.2 66.7 0.0Fossil Hominin (4) 20.0 0.0 5.0 75.0

RESULTS (B): Canonical Discrimant Analysis

RESULTS (B): Canonical Discrimant Analysis

RESULTS (B): Canonical Discrimant Analysis

RESULTS (B): Canonical Discrimant Analysis

RESULTS (B): CV1 shape change (64.77%)

Summary

Principal Components Analysis• LB1’s mandible morphology clusters with

fossils• Microcephalic and Cretin mandibles within

range of non-pathological variation (including adults and subadults)

• Chin, gonion, alveolus height, symphyseal morphology distinguish fossils from modern human group

Canonical Discriminant Analysis• LB1 classified as 98.8% fossil hominin• Microcephalics and Cretins overlap most

with subadult morphology• LB1 is most similar to early fossil Homo,

however more samples needed to verify

Conclusions• LB1 is NOT a microcephalic or a cretin

• Anatomically modern human mandibles with growth-deficiency pathologies do not develop fossil hominin morphology

• Some, though not all, retain subadult morphology• Microcephalic and cretin (Hypothyroidism) mandibles extend

modern human shape space away from fossil hominins from the Middle Pleistocene and older

• Mandible morphology of LB1 and LB6 fall outside the range of normal and pathological modern human variation

• The results support the new species designation, Homo floresiensis, for the Liang Bua material

Acknowledgements• American Museum of Natural History, New York

• Ian Tattersall• Gisselle Garcia

• Musee de l’Homme, Paris• Philippe Mennecier• Veronique Laborde• Aurelie Fort

• Naturalhistoriche Museum, Basel• Gerhard Hotz

• Dept. of Anthropology, University of Geneva

• Royal Belgian Institute of Sciences, Brussels• Patrick Semal

• Royal College of Surgeons, Edinburgh• Andrew Connell

• National Science Foundation Graduate Research Fellowship

• Australian Research Council

• Thomas Sutikna, E Wahyu Saptomo, Michael Morwood

ARKENAS