Tall molars did not evolve from eating grass
It is a classic tale of evolutionary biology that tall or high-crowned molars (hypsodonty) in mammals only evolved when grasslands evolved.1
This supposedly took place during the Cenozoic2 when the cooling climate caused forests to change into extensive grasslands. It was thought the high-crowned molars developed as a result of wear from eating grass containing phytoliths (silica-rich granules).
Worn-out teeth supposedly caused the mammals to develop taller, longer-lasting teeth (figure 1). New evolutionary research calls into question this classic tale.
Hypsodonty out of phase with grasslands
Researchers using Cenozoic dating methods for various groups of ungulates (hoofed animals), as well as rodents and rabbits, discovered that the origin of hypsodonty was out of phase with the supposed spread of grasslands in the United States’ Midwest. Some animals developed high crowns before and some after the supposed ‘evolution’ of the grassland. Moreover, many mammal families did not evolve tall teeth at all. Therefore, the researchers have mostly abandoned the classic tale but have adopted a new hypothesis. They now claim high-crowned teeth were not due to the evolution of grasslands but from the effects of grit and soil:
“These results indicate that hypsodonty was not a simple adaptation for eating grass, and may have originated in some clades [groups of animals] to counteract the ingestion of grit and soil.”3
This hypothesis seems even less plausible because previously the abrasive agent was in the food, while in the new idea the abrasive agent is the soil, which would rarely be consumed.
The first lesson learned from this story is to be aware of the speculation advanced for the purpose of maintaining the evolutionary status quo. The hypothesis of evolution often requires ‘just so stories’ to explain difficulties when interpreting fossils, radiometric dating, or paleoenvironments. In the biological sciences in particular, recourse is often had to the assumption that non-existent genetic information will somehow be created in response to a perceived environmental need.
Secondly, we must always be alert to the fact that circular reasoning is common within evolutionary biology and paleontology.3,4,5,6 Just as with uniformitarian paleoenvironmental interpretations,7 we must be aware of circular reasoning and the reinforcement syndrome, the tendency to keep evolutionary concepts going with ‘further research’. Circular reasoning is shown in the issue of hypsodonty in that evolutionists have used it as diagnostic of a grassland, when there is no paleobotanic evidence.1 They have also used hypsodonty as a measure of aridity:
“Fossil ungulate assemblages have recently been employed as palaeo-precipitation indicators, with community hypsodonty levels being a key character for measuring aridity … .”1
It would not be surprising if the ‘degree of hypsodonty’ has been used to ‘date’ a particular mammal group during the Cenozoic, but the main article gave no indication of this. The assumed paleotemperature, based on the particular fossil assemblage, has been used as input to place the fossils within the Cenozoic era, which presumably was generally cooling throughout.7,8
References and notes
- Jardin, P.E., Janis, C.M., Sahney, S. and Benton, M.J., Grit not grass: concordant patterns of early origin of hypsodonty in Great Plains ungulates and Glires, Palaeogeography, Palaeoclimatology, Palaeoecology 365–366:1–10, 2012 | doi:10.1016/j.palaeo.2012.09.001. Return to text.
- The geological timescale and subdivisions are used for discussion purposes only. Return to text.
- Oard, M.J., Paleocene dinosaurs and the reinforcement syndrome, J. Creation 17(3):5–8, 2003; creation.com/paleocene-dinosaurs. Return to text.
- Oard, M.J., End-Mesozoic extinction of dinosaurs partly based on circular reasoning, J. Creation 15(2):6–7, 2010; creation.com/dino-extinction. Return to text.
- Oard, M.J., Dinosaur Challenges and Mysteries: How the Genesis Flood Makes Sense of Dinosaur Evidence—Including Tracks, Nests, Eggs, andScavenged Bonebeds, Creation Book Publishers, Powder Springs, GA, pp. 156–162, 2011. Return to text.
- Oard, M.J., The reinforcement syndrome ubiquitous in the earth sciences, J. Creation 27(3):13–16, 2013; creation.com/reinforcement-syndrome. Return to text.
- Oard, M.J., Beware of paleoenvironmental deductions, J. Creation 13(2):13, 1999; creation.com/paleoenvironmental-deductions. Return to text.
- Oard, M.J., Is the K/T the post-Flood boundary?—part 2: paleoclimates and fossils, J. Creation 24(3): 87–93, 2010; creation.com/kt-boundary-flood-2. Return to text.