Paleo-Ontogenetic Growth Curves: Evidence for Extreme Past Animal Longevity? 9th International Conference on Creationism: July 16-19, 2023 “Old” Adolescent Sharks Based on vertebrae growth rings, paleontologists estimate that a Cretaceous Ptychodus shark was 30 years old at time of death. One would expect the spacing between these growth rings to become narrower as the shark approached adulthood. Yet this narrowing pattern was not present, suggesting that the already 4-7 meter long shark was still a rapidly-growing adolescent. Growth rings in Ptychodus shark vertebrae. Image Credit: Jambura, P. L. and J. Kriwet. 2020. Creative Commons Attribution License. “. . . We calculated a size of 4-7 meters and an age of 30 years for the examined shark. It’s astonishing that this shark was not yet mature when it died despite its rather old age . . . . [T]his shark doesn’t show any signs of flattenings or inflections in the growth profile, meaning that it was not mature –a teenager, if you want. This suggests that these sharks grew even larger and older.” Patrick L. Jambura, paleontologist Giant ‘teenager’ shark from the dinosaur era identified from vertebrae remains. Phys.org. Posted April 23, 2020 at phys.org, accessed March 23, 2023. Jambura, P. L. and J. Kriwet. 2020. Articulated remains of the extinct shark Ptychodus (Elasmobranchii, Ptychodontidae) from the upper Cretaceous of Spain provide insights into gigantism, growth rate and life history of ptychodontid sharks. PLoS ONE 15 (4): 1-16. Moreover, Shimada et al. (2021) used 46 vertebrae growth rings and inferred sizes from the largest two known Otodus megalodon teeth to construct the theoretical megalodon growth curve shown above. The growth rings belonged to an apparently 46-year-old adolescent megalodon. Although the size estimate is likely too high (see downward pointing question mark), a face-value interpretation of their growth curve implies that this megalodon would have taken 498 years to reach 95% of its total estimated length. After Figure 2a in Shimada et al. (2021). Shimada, K. et al. 2021. Ontogenetic growth pattern of the extinct megatooth shark Otodus megalodon–implications for its reproductive biology, development, and life expectancy. Historical Biology 33(12): 3254-3259. “Extreme Longevity” in Cenozoic Marine Bivalves Buick and Ivany (2004) counted internal growth rings of 12 Eocene Cucullaea raeaclams from Seymour Island, Antarctica and concluded that C. raea lifespans routinely exceeded 100 years. Likewise, Moss et al. (2017) concluded that 11 species of Late Cretaceous and Paleogene bivalves, also from Seymour Island, exhibited “extreme longevity” compared to modern bivalves. These findings were especially remarkable because, according to uniformitarian thinking, Antarctic waters were generally warmer during the Cretaceous and Paleogene, and many creationists would concur that pre-Flood oceans were warmer than today. But warm water is usually associated with shorter lifespans in marine bivalves. Thus one would expect shorter lifespans in the fossil versions, yet the opposite was the case. “All of the species examined reached ages greater than 20 years, and 10 of the 11 had life spans greater than 50 years . . . . While a number of modern taxa can attain life spans in excess of 50 years, the modal value of maximum reported life span for bivalve species today is 3 years . . . . The shortest-lived species measured from Seymour Island reached life spans of at least 22 years.” Moss et al. (2017) Moss, D. K. et al. 2017. High-latitude settings promote extreme longevity in fossil marine bivalves. Paleobiology 43 (3): 365-382. Buick, D. P. and L. C. Ivany. 2004. 100 years in the dark: Extreme longevity of Eocene bivalves from Antarctica. Geology 32 (10): 921-924. Kirby (2001) found a dramatic decrease in Recent and late Pleistocene oyster lifespans and sizes compared to oysters of the same genus in Miocene strata. His results were obtained with California, Virginia, and North Carolina Crassostreaoysters all collected from between 34.6 and 36.8° North latitude. After Kirby’s Figure 3B. Kirby, M. X. 2001. Differences in growth rate and environment between Tertiary and Quaternary Crassostreaoysters. Paleobiology 27 (1): 84-103. Future Work I hope to collaborate with creationist biologists, paleo-experts and statisticians to study this issue much more thoroughly. Given the ubiquity of bivalves (clams) in the fossil record, it might be possible for creationists to conduct our own original research in this area, provided that creationists who own fossil clams are willing to sacrifice them in order to count internal bands (counting is a destructive process, unfortunately). I have also found statements within the literature that the “oldest” Cenozoic birds were taking as much as three years to reach maturity, whereas most of today’s birds take a year or less. This too needs to be researched. Abstract One of the Bible’s most ridiculed claims is its matter-of-fact assertion that humans once routinely experienced lifespans of 900 years. Thus, the possibility of fossil evidence partially corroborating the Bible’s claim should be of great interest to creationists. Paleo-ontogenetic growth curves for crocodylian, shark, and marine bivalve fossils show indirect and/or direct evidence of increased animal longevity in the pre-Flood and immediate post-Flood worlds. Longer Childhood, Longer Life Studies of extant organisms have shown that organisms that take longer to reach maturity live longer than similar organisms that reach maturity more quickly. This has been demonstrated for many terrestrial vertebrates (including birds), marine bivalves, and some fishes. Hence, evidence that past organisms took longer to mature than their modern-day counterparts is indirect evidence for greater past longevity. In this vein, it is striking that, excluding Adam, the earliest age at which a Genesis 5 patriarch is listed as having a son is 65 years. It’s possible that antediluvian humans did not reach sexual maturity until 60 or 70 years of age. That the Bible may associate their amazing longevity with greater ages at sexual maturity may be a subtle correct detail that testifies to the truthfulness of Scripture’s claims in this regard. Also, there is some evidence that longer lifespans are positively correlated with larger sizes at maturity. Hence, both the larger sizes and apparently longer maturation times of past animal forms could be evidence for greater animal longevity in the past. Ricklefs, R. E. 2010. Life-history connections to rates of aging in terrestrial vertebrates. PNAS 107 (22): 10314-10319. Slower Growth in Past Alligatoroids Many, if not all, extant animals exhibit a “sigmoid” growth curve with rapid growth in early life that later “levels off”, and slows or completely stops in later life. The same appears to be true for animals of the past. Although growth in extant crocodiles and alligators typically slows down by the ages of 2030 years, some extinct crocodylian forms were apparently still experiencing relatively rapid growth at 40 and 50 years of age. Data reconstructed from Erickson and Brochu (1999) and Chabreck and Joanen (1979). Erickson, G. M. and C. A. Brochu. 1999. How the ‘terror crocodile’ grew so big. Nature398 (6724): 205-206. Sereno, P. C. et al. 2001. The giant Crocodyliform Sarcosuchus from the Cretaceous of Africa. Science294 (5546): 1516-1519. Chabreck, R. H. and T. Joanen. 1979. Growth Rates of American Alligators in Louisiana. Herpetologica35 (1): 51-57. Shark Image Credit: Mostafa Elturkey (Public Domain) Alligator Image Credit: Gareth Rasberry, CCA-SA 3.0 Unported Jake Hebert, Ph.D. Research Scientist Institute for Creation Research Dallas, TX 75229 jhebert@ICR.org
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