The brain of Homo habilis: Three decades of paleoneurology

In 1987, Phillip Tobias published a comprehensive anatomical analysis of the endocasts attributed to Homo habilis, discussing issues dealing with brain size, sulcal patterns, and vascular traces. He suggested that the neuroanatomy of this species evidenced a clear change toward many cerebral traits associated with our genus, mostly when concerning the morphology of the frontal and parietal cortex. After more than 30 years, the fossil record associated with this taxon has not grown that much, but we have much more information on cranial and brain biology, and we are using a larger array of digital methods to investigate the paleoneurological variation observed in the human genus. Brain volume, the size of the frontal lobe, or the gross hemispheric asymmetries are still relevant issues, but they are considered to be less central than before. More attention is instead being paid to the cortical organization, the relationships with the cranial architecture, and the influence of molecular or ecological factors. Although the field of paleoneurology can currently count on a larger range of tools and principles, there is still a general lack of anatomical information on many endocranial traits. This aspect is probably crucial for the agenda of paleoneurology. More importantly, the whole science is undergoing a delicate change, because of the growing influence of the social environment. In this sense, the disciplines working with fossils (and, in particular, with brain evolution) should take particular care to maintain a healthy professional situation, avoiding an excess of speculation and overstatement.

Flightless birds are not neuroanatomical analogs of non-avian dinosaurs

Background

In comparative neurobiology, major transitions in behavior are thought to be associated with proportional size changes in brain regions. Bird-line theropod dinosaurs underwent a drastic locomotory shift from terrestrial to volant forms, accompanied by a suite of well-documented postcranial adaptations. To elucidate the potential impact of this locomotor shift on neuroanatomy, we first tested for a correlation between loss of flight in extant birds and whether the brain morphology of these birds resembles that of their flightless, non-avian dinosaurian ancestors. We constructed virtual endocasts of the braincase for 80 individuals of non-avian and avian theropods, including 25 flying and 19 flightless species of crown group birds. The endocasts were analyzed using a three-dimensional (3-D) geometric morphometric approach to assess changes in brain shape along the dinosaur-bird transition and secondary losses of flight in crown-group birds (Aves).

Results

While non-avian dinosaurs and crown-group birds are clearly distinct in endocranial shape, volant and flightless birds overlap considerably in brain morphology. Phylogenetically informed analyses show that locomotory mode does not significantly account for neuroanatomical variation in crown-group birds. Linear discriminant analysis (LDA) also indicates poor predictive power of neuroanatomical shape for inferring locomotory mode. Given current sampling, Archaeopteryx, typically considered the oldest known bird, is inferred to be terrestrial based on its endocranial morphology.

Conclusion

The results demonstrate that loss of flight does not correlate with an appreciable amount of neuroanatomical changes across Aves, but rather is partially constrained due to phylogenetic inertia, evident from sister taxa having similarly shaped endocasts. Although the present study does not explicitly test whether endocranial changes along the dinosaur-bird transition are due to the acquisition of powered flight, the prominent relative expansion of the cerebrum, in areas associated with flight-related cognitive capacity, suggests that the acquisition of flight may have been an important initial driver of brain shape evolution in theropods.

Electronic supplementary material

The online version of this article (10.1186/s12862-018-1312-0) contains supplementary material, which is available to authorized users.

Lower pole anatomy and mid-renal-zone classification applied to flexible ureteroscopy: experimental study using human three-dimensional endocasts

PURPUSE

The aim of this study was to analyze the anatomy of the inferior pole collecting system and the mid-renal-zone classification in human endocasts applied to flexible ureteroscopy.

METHODS

170 three-dimensional polyester resin endocasts of the kidney collecting system were obtained from 85 adult cadavers. We divided the endocasts into four groups: A1--kidney midzone (KM), drained by minor calices (mc) that are dependent on the superior or the inferior caliceal groups; A2--KM drained by crossed calices; B1--KM drained by a major caliceal group independent of both the superior and inferior groups; and B2--KM drained by mc entering directly into the renal pelvis. We studied the number of calices, the angle between the lower infundibulum and renal pelvis and the angle between the lower infundibulum and the inferior mc (LIICA). Means were statistically compared using ANOVA and the unpaired T test (p < 0.05).

RESULTS

We found 57 (33.53 %) endocasts of group A1; 23 (13.53 %) of group A2; 59 (34.71 %) of group B1; and 31 (18.23 %) of group B2. The inferior pole was drained by four or more calices in 84 cases (49.41 %), distributed into groups as follows: A1 = 35 cases (41.67 %); A2 = 18 (21.43 %); B1 = 22 (26.19 %); and B2 = 9 (10.71 %). Perpendicular mc were observed in 15 cases (8.82 %). We did not observe statistical differences between the LIICA in the groups studied.

CONCLUSIONS

Collector systems with kidney midzone drained by minor calices that are dependent on the superior or on the inferior caliceal groups presented at least two restrictive anatomical features. The mid-renal-zone classification was predictive of anatomical risk factors for lower pole ureteroscopy difficulties.