The type specimen (LB1) of Homo floresiensis did not have Laron Syndrome

Abstract

The type specimen (LB1) of Homo floresiensis has been hypothesized to be a pathological human afflicted with Laron Syndrome (LS), a type of primary growth hormone insensitivity (Hershkovitz et al.: Am J Phys Anthropol 134 [2007] 198-208). Comparing measurements, photographs and three-dimensional, computed-tomography reconstructions of LB1 with data and diagnoses from the literature on LS, we critically evaluate numerous skull and postcranial traits that Hershkovitz et al. identified as being shared by LB1 and patients with LS. The statements regarding most of these traits are new to the clinical literature and lack quantitative support. LB1 and patients with LS differ markedly in the size and shape of the cranium; thickness and pneumatization of cranial bones; morphology of the face, mandible, teeth, and chin; form of the shoulder, wrist, and pelvis; and general body proportions including relative foot size. Claims that patients with LS are similar to LB1 in displaying protracted scapulae, short clavicles, low degrees of humeral torsion, flaring ilia, and curved tibiae are not supported by data or corroborating images. Some points of similarity (e.g., femoral neck-shaft angle, femoral bicondylar angle, and estimated stature) can be found in other hominins, and cannot be considered diagnostic. From our review and analysis, we conclude that LB1 did not suffer from LS.

Rare events in earth history include the LB1 human skeleton from Flores, Indonesia, as a developmental singularity, not a unique taxon

“…To make this point it is not necessary to diagnose any particular developmental abnormality or medical syndrome, contra the statement "We understand the cognitive dissonance that the discovery of Homo floresiensis has created in some scientific circles, and we encourage efforts to frame testable, alternative hypotheses to account for these surprising hominins. We submit that 'pathology,' however, is not a scientific explanation unless a differential diagnosis is made specific, plausible, and testable" (29). Ignoring the nonce ad hominem psychologizing (see also www.liangbuacave.org), the answer to that assertion already has been provided: "While the statement by Falk and colleagues seems superficially plausible, the formulation simply is fundamentally illogical.…”

“…The upper facial skeleton is reasonably well preserved save for nasal bones; this and the mandible are discussed separately in detail in Supporting Information, SI3. Preservation of the more fragile bones argues strongly against taphonomic deformation as the explanation for the unusual asymmetry (22,27), countering attempts to minimize the extent of asymmetry (28,29), with ref. 28 also exaggerating effects of taphonomic distortion.…”

Evolved developmental homeostasis disturbed in LB1 from Flores, Indonesia, denotes Down syndrome and not diagnostic traits of the invalid species Homo floresiensis

“…Perplexingly, all of the original observations on these factors (and others) were misleadingly reported (1). Craniofacial asymmetry was unremarked, whereas our own documentation of asymmetry (3) was disparaged without quantification (24) and then temporized for several years (25,26); endocranial volume first was reported as 380 mL, and stature as 1.06 m, both biased downward. We noted all these flaws (3,32), illustrating and quantifying craniofacial asymmetry, reporting endocranial volume as 430 mL, and recalculating stature as substantially taller (1.20-1.38 m) (3), noting the short, dysmorphic femora that influenced stature underestimation.…”

“…However, at least 50 syndromes express diminutive brain size and short stature, defining attributes of LB1 (3). Other telltale signs of abnormality are craniofacial asymmetry and early cranial suture closure (3,(22)(23)(24)(25)(26).…”

LB1 from Liang Bua, Flores: Craniofacial asymmetry confirmed, plagiocephaly diagnosis dubious

“…Here we limit ourselves to points raised by previous studies. Falk et al (2009) disputed our finding of asymmetry ''by electronically bisecting and mirror imaging the two halves of LB1's entire skull [their emphasis] along its midline, using the 3DCT data from the original LB1 specimen,'' and concluded ''Our results suggest an unremarkable and nonpathological degree of asymmetry in LB1's face, contrary to Jacob et al (2006).'' Their test of our work was not a close replication, since we provided not only the 2D mirror-images reproduced by Falk et al, but also replicable measurements from the midline to various precisely located landmarks.…”