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Emken S, Witzel C, Kierdorf U, Frölich K, Kierdorf H. A labeling study of dentin formation rates during crown and root growth of porcine mandibular first molars. Anat Rec (Hoboken) 2024; 307:2103-2120. [PMID: 38051150 DOI: 10.1002/ar.25358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2023] [Revised: 11/14/2023] [Accepted: 11/15/2023] [Indexed: 12/07/2023]
Abstract
We used fluorochrome labeling to study spatiotemporal variation of dentin apposition (DAR) and extension (DER) rates during crown and root formation of mandibular first molars from wild boar and domestic pigs. DAR was reconstructed along the course of dentinal tubules in four zones of the crown and in the upper root area. In all five zones, mean DAR increased during the first 30% to 40% of apposition, reaching highest values (22-23 μm/day) in the upper-lateral crown zone. Lowest values were recorded near the dentin-pulp interface (DPI). Typically, DARs in contemporaneously formed dentin areas were higher in more cuspally compared to more cervically/apically located zones. DER was high (>200 μm/day) in early postnatal crown dentin and then decreased markedly in cervical direction, with lowest values in the cervical crown zone. After this nadir, DER sharply increased in the upper 30% to 40% of the root extension, reaching values equaling (wild boar) or even surpassing (domestic pigs) those recorded in the upper lateral crown. After this peak, DER again decreased. While DAR did not differ markedly between wild boar and domestic pigs, the DER showed marked differences, both regarding maximum values (208.1 μm/day in wild boar, 272.2 μm/day in domestic pigs) and the timing of the root growth spurt, which occurred earlier in the domestic pigs. We consider the more rapid recruitment of secretory odontoblasts in domestic pigs (reflected by higher DER) a side effect of selection for rapid body growth during pig domestication.
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Affiliation(s)
- Simon Emken
- Department of Biology, University of Hildesheim, Hildesheim, Germany
| | - Carsten Witzel
- Department of Biology, University of Hildesheim, Hildesheim, Germany
| | - Uwe Kierdorf
- Department of Biology, University of Hildesheim, Hildesheim, Germany
| | - Kai Frölich
- Department of Biology, University of Hildesheim, Hildesheim, Germany
- Tierpark Arche Warder e.V., Warder, Germany
| | - Horst Kierdorf
- Department of Biology, University of Hildesheim, Hildesheim, Germany
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de Magalhães JP. The longevity bottleneck hypothesis: Could dinosaurs have shaped ageing in present-day mammals? Bioessays 2024; 46:e2300098. [PMID: 38018264 DOI: 10.1002/bies.202300098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 11/01/2023] [Accepted: 11/02/2023] [Indexed: 11/30/2023]
Abstract
The evolution and biodiversity of ageing have long fascinated scientists and the public alike. While mammals, including long-lived species such as humans, show a marked ageing process, some species of reptiles and amphibians exhibit very slow and even the absence of ageing phenotypes. How can reptiles and other vertebrates age slower than mammals? Herein, I propose that evolving during the rule of the dinosaurs left a lasting legacy in mammals. For over 100 million years when dinosaurs were the dominant predators, mammals were generally small, nocturnal, and short-lived. My hypothesis is that such a long evolutionary pressure on early mammals for rapid reproduction led to the loss or inactivation of genes and pathways associated with long life. I call this the 'longevity bottleneck hypothesis', which is further supported by the absence in mammals of regenerative traits. Although mammals, such as humans, can evolve long lifespans, they do so under constraints dating to the dinosaur era.
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Affiliation(s)
- João Pedro de Magalhães
- Genomics of Ageing and Rejuvenation Lab, Institute of Inflammation and Ageing, University of Birmingham, Birmingham, UK
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White HE, Tucker AS, Fernandez V, Portela Miguez R, Hautier L, Herrel A, Urban DJ, Sears KE, Goswami A. Pedomorphosis in the ancestry of marsupial mammals. Curr Biol 2023:S0960-9822(23)00457-8. [PMID: 37119816 DOI: 10.1016/j.cub.2023.04.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 02/27/2023] [Accepted: 04/05/2023] [Indexed: 05/01/2023]
Abstract
Within mammals, different reproductive strategies (e.g., egg laying, live birth of extremely underdeveloped young, and live birth of well-developed young) have been linked to divergent evolutionary histories. How and when developmental variation across mammals arose is unclear. While egg laying is unquestionably considered the ancestral state for all mammals, many long-standing biases treat the extreme underdeveloped state of marsupial young as the ancestral state for therian mammals (clade including both marsupials and placentals), with the well-developed young of placentals often considered the derived mode of development. Here, we quantify mammalian cranial morphological development and estimate ancestral patterns of cranial shape development using geometric morphometric analysis of the largest comparative ontogenetic dataset of mammals to date (165 specimens, 22 species). We identify a conserved region of cranial morphospace for fetal specimens, after which cranial morphology diversified through ontogeny in a cone-shaped pattern. This cone-shaped pattern of development distinctively reflected the upper half of the developmental hourglass model. Moreover, cranial morphological variation was found to be significantly associated with the level of development (position on the altricial-precocial spectrum) exhibited at birth. Estimation of ancestral state allometry (size-related shape change) reconstructs marsupials as pedomorphic relative to the ancestral therian mammal. In contrast, the estimated allometries for the ancestral placental and ancestral therian were indistinguishable. Thus, from our results, we hypothesize that placental mammal cranial development most closely reflects that of the ancestral therian mammal, while marsupial cranial development represents a more derived mode of mammalian development, in stark contrast to many interpretations of mammalian evolution.
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Affiliation(s)
- Heather E White
- Science Department, Natural History Museum, Cromwell Road, London SW7 5BD, UK; Centre for Craniofacial and Regenerative Biology, King's College London, Great Maze Pond, London SE1 9RT, UK; Division of Biosciences, University College London, Gower Street, London WC1E 6DE, UK.
| | - Abigail S Tucker
- Centre for Craniofacial and Regenerative Biology, King's College London, Great Maze Pond, London SE1 9RT, UK
| | - Vincent Fernandez
- European Synchrotron Radiation Facility, 71 rue des Martyrs, 38000 Grenoble, France
| | | | - Lionel Hautier
- Science Department, Natural History Museum, Cromwell Road, London SW7 5BD, UK; Institut des Sciences de l'Evolution, Université de Montpellier, CNRS, IRD, EPHE, Montpellier 34095, France
| | - Anthony Herrel
- UMR 7179, Centre National de la Recherche Scientifique/Muséum National d'Histoire Naturelle, Département Adaptations du Vivant, 55 rue Buffon, 75005 Paris, France
| | - Daniel J Urban
- Institute of Genomic Biology, University of Illinois, Urbana, IL 61801, USA
| | - Karen E Sears
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Anjali Goswami
- Science Department, Natural History Museum, Cromwell Road, London SW7 5BD, UK; Division of Biosciences, University College London, Gower Street, London WC1E 6DE, UK
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Smith TM, Arora M, Bharatiya M, Dirks W, Austin C. Brief Communication: Elemental Models of Primate Nursing and Weaning Revisited. AMERICAN JOURNAL OF BIOLOGICAL ANTHROPOLOGY 2023; 180:216-223. [PMID: 37406034 PMCID: PMC10099337 DOI: 10.1002/ajpa.24655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Revised: 10/25/2022] [Accepted: 11/01/2022] [Indexed: 07/07/2023]
Abstract
Objectives Intra-tooth patterns of trace elements barium (Ba) and strontium (Sr) have been used to infer human and nonhuman primate nursing histories, including australopithecine and Neanderthal juveniles. Here we contrast the two elemental models in first molars (M1s) of four wild baboons and explore the assumptions that underlie each. Materials and Methods Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was employed to create comprehensive calcium-normalized barium and strontium (Ba/Ca, Sr/Ca) maps of M1 enamel and dentine at 35 micron resolution. Results Postnatal Ba/Ca values were typically high, peaking ~0.5 years of age and then decreasing throughout M1 crown formation; all four individuals showed minimal Ba/Ca values between ~1.2-1.8 years, consistent with field reports of the cessation of suckling. Enamel Sr/Ca did not support patterns of previous LA-ICP-MS spot sampling as the enamel rarely showed discrete Sr/Ca secretory zonation. Increases in Sr/Ca appeared in coronal dentine beginning ~0.3 years, with varied peak value ages (~0.7-2.7 years) and no evidence of a predicted postweaning decline. Discussion Inferences of baboon weaning ages from initial Ba/Ca minima are more congruent with behavioral observations than Sr/Ca maxima; this is consistent with studies of captive macaques of known weaning ages. Elemental variation is more apparent in the coronal dentine than the enamel of these baboons, which may relate to its more rapid mineralization and protection from the oral environment. Inferences of nursing histories from enamel Sr/Ca patterns alone should be reconsidered, and elevated values of Ba/Ca and Sr/Ca in teeth formed after weaning require further study.
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Affiliation(s)
- Tanya M. Smith
- Griffith Centre for Social and Cultural ResearchGriffith UniversityNathanAustralia
- Australian Research Centre for Human EvolutionGriffith UniversityNathanAustralia
| | - Manish Arora
- Department of Environmental Medicine and Public HealthIcahn School of Medicine at Mount SinaiNew YorkNew YorkUSA
| | - Maya Bharatiya
- Griffith Centre for Social and Cultural ResearchGriffith UniversityNathanAustralia
- Australian Research Centre for Human EvolutionGriffith UniversityNathanAustralia
| | - Wendy Dirks
- Department of AnthropologyDurham UniversityDurhamUK
| | - Christine Austin
- Department of Environmental Medicine and Public HealthIcahn School of Medicine at Mount SinaiNew YorkNew YorkUSA
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