Creationism in Crisis - How Elephants Got Their Trunks and Tusks 20 Million Years Before 'Creation Week' - No Magic Required

Artist's impression of Platybelodon grangeri

Credit: Tim Bertelink via Wikimedia (CC BY-SA 4.0)

Platybelodon grangeri (artist's impression)

How shifting climates may have shaped early elephants’ trunks | For the press | eLife

As expected of scientific research papers, this one deals with events that occurred in that vast expanse of time before creationists think Earth was created, when 99.97% of Earth's history occurred.

This one, published open access in eLife, explains how the ancestors of modern elephants and their recently extinct relatives, the mammoths, got their long flexible trunks and used them for their unique feeding method.

The paper by lead author, Chunxiao Li, and colleagues from the Key Laboratory of Vertebrate Evolution and Human Origins of the Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China, and including Burt Wolff of the Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, FL, USA and Fajun Sun of the Department Environmental Science & Technology, University of Maryland, MD, USA, "combines multiple analyses to reconstruct feeding behaviours in the extinct longirostrine elephantiforms - elephant-like mammals characterised by elongated lower jaws and tusks."

It seems that, as they grew larger, for reasons not yet fully understood, but possibly to give a larger 'vat' in which to ferment their high-cellulose diet, these early ancestors of the elephants had to evolve a longer jaw to reach the grasses and shrubs on which they grazed. The trunk extended as part of this process of facial elongation. This in turn created the opportunity for the end of the truck to play a part in holding the plants as they were cut off by the incisor teeth at the end of the lower jaw. This was more of an advantage in the open grasslands that Platybelodon inhabited, so, when climate change meant loss of habitat and eventual extinction for the two related gomphotheres, Platybelodon's prehensile trunk gave it enough advantage to survive.

A press release by eLife explains the research and its significance for understanding how elephants got their trunks:

Visualisation of the Platybelodon, showing the long mandible and coiling, grasping trunk. The Platybelodon may have been the first proboscidean to evolve this grazing behaviour.

Image credit: Chunxiao Li (CC BY 4.0)

Longirostrine gomphotheres are part of the proboscidean family - a group of mammals including elephants and known for their elongated and versatile trunks. Longirostrine gomphotheres are notable as they underwent a prolonged evolutionary phase characterised by an exceptionally elongated lower jaw, or mandible, which is not found in later proboscideans. It is thought that their elongated mandible and trunk may have co-evolved in this group, but this change among early to late proboscideans remains incompletely understood.

During the Early to Middle Miocene, gomphotheres flourished across Northern China. Across species there was huge diversity in the structure of the long mandible. We sought to explain why proboscideans evolved the long mandible and why it subsequently regressed. We also wanted to explore the role of the trunk in these animals’ feeding behaviours, and the environmental background for the co-evolution of their mandibles and trunks.

Dr. Chunxiao Li, lead author
Postdoctoral researcher
University of Chinese Academy of Sciences, Beijing, China.

Li and colleagues used comparative functional and eco-morphological investigations, as well as a feeding preference analysis, to reconstruct the feeding behaviour of three major families of longirostrine gomphotheres: Amebelodontidae, Choerolophodontidae and Gomphotheriidae.

To construct the feeding behaviours and determine the relation between the mandible and trunk, the team examined the crania and lower jaws of the three groups, sourced from three different museums. The structure of the mandible and tusks differed across the three groups, indicating differences in feeding behaviours. The mandibles of Amebelodontidae were generally shovel-like and the tusks were flat and wide. Gomphotheriidae had clubbed lower tusks and a more narrow mandible, while Choerolophodontidae completely lacked mandibular tusks and their lower jaw was long and trough-like.

Next, the team conducted an analysis of the animals’ enamel isotopes to determine the distribution and ecological niches of the three families. The results indicated that Choerolophontidae lived in a relatively closed environment, whereas Platybelodon, a member of the Amebelodontidae family, lived in a more open habitat, such as grasslands. Gomphotheriidae appeared to fill a niche somewhere in between these closed and open habitats.

A Finite Element analysis helped the team determine the advantages and disadvantages of the mandible and tusk structure between each group. Their data indicated that the Choerolophodontidae mandible was specialised for cutting horizontally or slanted-growing plants, which may explain the absence of mandibular tusks. The Gomphotheriidae mandible was found to be equally suited for cutting plants growing in all directions. Platybelodon had structures specialised for cutting vertically growing plants, such as soft-stemmed herbs, which would have been more common in open environments.

The three families also showed differences in their stages of trunk evolution, which could be inferred from the narial structure - the region surrounding the nostrils. The narial region in Choerolophodontidae suggested that they had a relatively primitive, clumsy trunk. In Gomphotheriidae, the narial region was most similar to modern day elephants, suggesting they had a relatively flexible trunk. The trunks of Platybelodons may be the first example of a proboscidean trunk with the ability to coil and grasp. The evolutionary level of the trunk appeared to relate to the ability of the mandible to cut horizontally, strongly suggesting a co-evolution between the trunk and the mandible in longirostrine gomphotheres.

Our findings demonstrate that multiple eco-adaptations have contributed to the diverse mandibular structure found in proboscideans. Initially, the elongated mandible served as the primary feeding organ in proboscideans, and was a prerequisite for the development of the extremely long trunk. Open-land grazing drove the development of trunk coiling and grasping functions, and the trunk then became the primary tool for feeding, leading to the gradual loss of the long mandible. In particular, Platybelodons may have been the first proboscidean to evolve this grazing behaviour.

Professor Dr. Shi-Qi Wang, senior author
Key Laboratory of Vertebrate Evolution and Human Origins
Chinese Academy of Sciences.

During the Mid-Miocene Climate Transition, which caused regional drying and the expansion of more open ecosystems, Choerolophodontidae experienced a sudden regional extinction and Gomphotheriidae numbers also declined in Northern China. The study suggests that the development of the coiling and grasping trunk in Platybelodon allowed this group to survive in greater numbers in their open environments. This may also explain why other animals with trunks, such as tapirs, never developed such dextrous trunks as elephants, as they never moved into open lands.

Our cross-disciplinary team is dedicated to introducing multiple quantitative research methods to explore paleontology. Modern computational mechanics and statistics have injected new vitality into traditional fossil research.

Associate Professor Ji Zhang, Co-author
Professor of structural engineering
Huazhong University of Science and Technology, Wuhan, China.

The main limitation of this work is the lack of discussion comparing the team’s results with the development of gigantism and long limbs in proboscideans from the same period, according to eLife’s editors. The authors add that such analysis could add to our understanding of how changing feeding behaviours related to wider differences in the animals’ body shapes and sizes during this time.

Technical details are given in the Abstract and Introduction to the team's paper in eLife:

Abstract

The long-trunked elephantids underwent a significant evolutionary stage characterized by an exceptionally elongated mandible. The initial elongation and subsequent regression of the long mandible, along with its co-evolution with the trunk, present an intriguing issue that remains incompletely understood. Through comparative functional and eco-morphological investigations, as well as feeding preference analysis, we reconstructed the feeding behavior of major groups of longirostrine elephantiforms. In the Platybelodon clade, the rapid evolutionary changes observed in the narial region, strongly correlated with mandible and tusk characteristics, suggest a crucial evolutionary transition where feeding function shifted from the mandible to the trunk, allowing proboscideans to expand their niches to more open regions. This functional shift further resulted in elephantids relying solely on their trunks for feeding. Our research provides insights into how unique environmental pressures shape the extreme evolution of organs, particularly in large mammals that developed various peculiar adaptations during the late Cenozoic global cooling trends.

eLife assessment

This study presents fundamental findings on the evolution of extremely elongated mandibular symphysis and tusks in longirostrine gomphotheres from the Early and Middle Miocene of northern China. The integration of multiple methods provides compelling results in the eco-morphology, behavioral ecology, and co-evolutionary biology of these taxa. In doing so, the authors elucidate the diversification of fossil proboscideans and their likely evolutionary responses to late Cenozoic global climatic changes.

Introduction

Proboscideans are known for their exceptionally elongated and versatile trunks (Shoshani, 1998). However, unlike modern elephants, proboscideans underwent a prolonged evolutionary phase characterized by the presence of greatly elongated mandibular symphysis and mandibular tusks (Cuvier and Laurillard, 1850; Schulz et al., 2022; Shoshani, 2000). This elongation can be traced back to the Late Oligocene species Palaeomastodon and Phiomia, which are among the earliest elephantiforms, and continued through to the Late Miocene Stegotetrabelodon, a stem elephantid (Andrews, 1906). Extreme longirostriny, a feature observed in fossil and modern fishes, reptiles, and birds, was relatively rare among terrestrial mammals and its occurrence in large-bodied proboscideans is particularly intriguing. Particularly, during the Early and Middle Miocene (approximately 20-11 Ma), the morphology of mandibular symphysis and tusks exhibited remarkable diversity, with over 20 genera from six families (Deinotheriidae, Mammutidae, Stegodontidae, Gomphotheriidae, Amebelodontidae, and Choerolophodontidae) displaying variations (Tassy, 1996). Why did proboscideans have evolved such a long mandible of so diversified morphology? How did fossil proboscideans use their strange mandibular symphysis and tusks, and what was the role of trunk in their feeding behavior? Finally, what was the environmental background for the co-evolution of their mandible and trunks, and why did proboscideans finally lose their long mandible? These important issuers on proboscideans evolution and adaptation remain poorly understood. Addressing these significant aspects of proboscidean evolution and adaptation requires comprehensive investigations into the functional and eco-morphology of longirostrine proboscideans.

Fig 1.

Morphology of the narial region and mandible of three gomphothere families compared with an extant elephant, and the elephantiformes phylogeny. A, Phylogenetic reconstruction of major longirostrine elephantiforms at the species level based on the Bayesian tip-dating method. The node support (the number at each node) is the posterior probability, and the bars represent chronologic ranges of each taxon. B-D, Representative cranium and mandible specimens of the three gomphothere families, including IVPP V22780, cranium, and IVPP V22781, mandible, of Gomphotherium tassyi (B), “Gomphotheriidae”, from Heijiagou Fauna, Tongxin region; HMV 0930, cranium and associated mandible of Platybelodon grangeri (C), from Zengjia Fauna, Linxia Basin; and IVPP V23457, cranium and associated mandible of Choerolophodon chioticus (D), from Middle Miaoerling Fauna, Linxia Basin. E-H, Narial morphology of gomphotheres and elephantids in dorsal view, including IVPP OV733, Elephas maximus (E), a living elephantid; HMV 0930, Platybelodon grangeri (F); IVPP V22780, Gomphotherium tassyi (G); and IVPP V23457, Choerolophodon chioticus (H). I-M, Mandibular morphology of gomphotheres. I and J, Mandibular symphysis and tusks of HMV 0930, Platybelodon grangeri, in dorsal (I) and distal (J) views. K, Mandibular symphysis and tusks of IVPP V22781, Gomphotherium tassyi (K), in dorsal view. L, Mandibular symphysis of IVPP V25397, Choerolophodon chioticus (L), showing the deep slits at both sides of the distal alveolar crests in dorsal view. M, Reconstruction of keratinous cutting plates in the slits, in dorsolateral view. Anatomic abbreviations: ce, cutting edge of the distal mandibular tusk in Platybelodon; kcp, reconstructed keratinous cutting plates in Choerolophodon; nb, nasal process of nasal bone; mc, slit or groove for mesethmoid cartilage insertion (white in color); pf, perinasal fossa; ps, prenasal slope in Platybelodon; s, slit for holding kcp in Choerolophodon.

Fig 3.

Finite element analyses of feeding behaviors among three longirostrine gomphothere families and reconstruction of their feeding ecology. A-C, von Mises stress color maps of Choerolophodon (A), Gomphotherium (B), and Platybelodon (C) models, with the full muscle forces exerted, and an additional 5000 N external vertical force applied on the distal end of the mandibular symphysis. D, Strain energy curves of the three mandibles under the following three steps: 1, muscle forces linearly exerted; 2, a 5000 N external vertical force suddenly applied on the distal end; and 3, the 5000 N external force gradually changed from vertical to horizontal. E, Sum of equivalent plastic strain from total elements (SEPS) of twigs cut by mandible models in three different directions (i.e., twig horizontal, 45° oblique, and vertical). Larger SEPS values indicate higher efficiency of twig cutting. F, Scenery reconstruction of feeding behaviors of the three longirostrine gomphothere families (by X. Guo), represented by Choerolophodon (Choerolophodontidae), feeding in a closed forest, Gomphotherium (“Gomphotheriidae”), feeding at the margin between the closed forest and open grassland, and Platybelodon (Amebelodontidae), feeding on open grassland. G, Detailed 3D reconstruction of Platybelodon feeding by grasping the grass-blades using their flexible trunk and cutting the grass blades using the distal edge of their mandibular tusks.

Fig 4.

Evolutionary levels of narial region (A) and of characters in relation to horizontal cutting (B). Value in A was PC1 of characters 54-57 (see Supplementary Appendix S1 and Data S1); and that in B was PC2 of characters 5, 9, 11, 72, and 77. Note that the clade of Platybelodon (marked by an asterisk) shows high evolutionary levels and that of Choerolophodontidae (marked by a circle) shows low evolutionary levels in both character-combines, strongly suggesting the co-evolution of narial morphology and horizontal cutting behavior.

Chunxiao Li, Tao Deng, Yang Wang, Fajun Sun, Burt Wolff, Qigao Jiangzuo, Jiao Ma, Luda Xing, Jiao FuJi Zhang, Shi-Qi Wang, (2023)
Longer mandible or nose? Co-evolution of feeding organs in early elephantiforms
eLife 12: RP90908 https://doi.org/10.7554/eLife.90908.1

Copyright: © 2023 The authors.
Published by eLife Sciences Publications Ltd. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

Amongst the thing for creationists to ignore, lie about or accuse the scientists of being part of a vast conspiracy over are:

1. The fact that the fossils of these ancestral elephants are found in rocks dated to between 11 and 20 million years old.
2. Even if 1 above can be explained away with unevidenced change in nuclear decay rates without changing the weak and strong nuclear forces to such an extent that life would have been impossible when it was allegedly created by magic, 10,000 years ago, followed by the assertion that all fossils died in a global genocidal flood 4,000 years ago, there is the problem of the geological column: these fossils are never found in or above the same strata as modern species, but always below them.
3. Then there is the evidence that the scientist showed not the slightest doubt that the Theory of Evolution was less than adequate to explain the facts.

So, it looks very much like what we have here is evidence that these creatures lived some 11-20 million years before 'Creation Week', and then evolved into the extinct mammoths, mastodons and mammuts and the three extant species of elephant, and yet another science paper which, like almost all biology, palaeontology, geology and cosmology papers, refutes the childish creationist superstition.

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