Evolution of teeth in vertebrates

Comparative Anatomy of teeth and evolutionary aspects of teeth.
From where did the teeth come from? How did they evolve? Which factors have contributed to this process?

1. Comparative anatomy of teeth and evolution of it VNMU 2019 Reporters: Turgut Novruzlu , Reem Alrefai Scientific supervisor: prof . Sergey Shuvalov MD, PhD

2. ORIGIN OF TEETH IN VERTEBRATES The first occurrence of tooth like structures was found in posterior pharynx of jawless fishes ( Romundina 400-419 million years ago) There are 2 actual theories about the reason why teeth have occurred in first place 1. Oral teeth evolved with jaws for predation and mastication 2. Teeth have appeared as external dental armor for protection from predation.

3. Changes in shape of dentition Reduction of size of teeth over 2000 years

4. Reasons for changes The evolution of human masticatory complex is stron g ly related to diet, the use of tools and fire. And the current look of our teeth are nothing like what we used to have. There are several factors that were changed by time; Change in our habitat, use of fire, the fact that after humans started consume food that they acquire from agriculture and etc.

5. Evolution of alveolar socket Bones grow in shape and size in response to frequent and habitual strain and loose mass in absence of force. This explains epigenetic trait in size of alveolar process. In early man, the teeth were big, and alveolar sockets were large to hold on the teeth, but as the forces for chewing reduced, the size of teeth and alveoli decreased as well

6. Special attention to teeth of lampreys Teeth of lampreys represent a very early stage in evolution of teeth of vertebrates. Each teeth consists of a thick, horny, epithelial thorn with a pulp within, which is ready to grow another thorn when it is broken. Lampreys belong to class Cyclostomata which literally means round mouthed. And they are polyphyodont Polyphyodontia means that specie has more than 2 sets of teeth

7. Ancient ancestors Predecessors of vertebrates probably fed upon small organisms and organic matter, which were scooped into mouth cavity and may have been passed along stomach by of lashing of cilia. However, there is another predecessor, namely Lamprey ( Ostracoderm ) from order of Anaspida , which the body form seems adapted for fast movement through water, and in which the mouth is strengthened by a bony strip with a knob on its front end.

8. Changes in palatal arch The reduction in size of all teeth, especially the canines, has been an important factor in shortening the palatal arch. The change of of palatal arch from shaped type of anthropoids, with wide space between Canines , to the short human form of palate with narrow space between canines.

9. Palatal arches of Anthropoids and Man -The upper lateral incisors in anthropoids as a rule are more primitive in retaining the bluntly pointed tips. -A significant difference between dentition of man his anthropoid cousins lie in the fact, that in man the canine teeth even in milk set are much reduced in size. -While, in the anthropoids, especially males, the canines form large sharp-tipped tusks -Our molars tend to be smaller as they go posteriorly and they rotate slightly, while in most of other apes this phenomena is absent

10. Genus homo Loss of gap between canines and premolars are of great importance This is clear evidence of decrease in tough fiber and less reliance on meat in genus Homo Australopithecines, who had large and flat molar teeth were suitable for hard and brittle food like some fruits, nuts, flowers and buds. Also these species started to use tools to cut and grind meat, so the need for adaptive characteristics such as strong jaw bones, large canines and stronger masticatory muscles started to decrease

11. Mutations in case of decreased natural selection Reduction of jaw size is strongly related to transition from hunter gatherer community to a fully Neolithic (agriculturist) community. In the absence of natural selection, mutations will be the main force acting towards a reduction of structural size and comlixity of teeth and other organs. Cooking is another factor on lessening the need for carnivore adaptation. It is knows that australopithecines used flake tools.

12. Modern descendant of ostracoderms

13. Comparative anatomy of the human palate Determining the course of evolution in mammals and man, there is clear evidence of progressive changes in palatal region. In early amphibians the air taken into olfactory chamber was passed through a pair of tubes opening by the into the mouth , and they were literally swallowing the inspired air However, in early mammal-like reptiles the choanae opened into a depression lying considerable above the general level of tooth-bearing margins of the upper jaw and it was the beginning of a fleshy palate.

14. Human embryo passes through a stage whereby its olfactory capsules look like those of sharks

15. Traces of first appearance of teeth In early vertebrates in the margins of oral cavity, there were teeth in a conical shape, which were serving as tool to hold the food inside of oral cavity. However, in some other vertebrates which have evolved further, they serve to tear apart bolus into smaller pieces. Evolution of teeth starts from appearance of ectodermal thickening, which had some-what connective tissue like appearance to the skin.

16. Development of main forms of permanent teeth in mammals

17. Wisdom teeth and evolutionary traces Our species used to have larger jaws and they could contain more teeth. So wisdom teeth were useful for chewing grass stronger and faster. But now they are just vestigial organ.  However by time we migrated from trees to land, surroundings where our anthropoid  ancestors could not find fruits and grass to eat.  So we started to consume meat. Meat is totally different than grass, nutritionally and by its consistency. So our jaw size started to decrease, while our cranial cavity size have increased to make more space for brain. And after we started to use fire, there was no need to have extremely strong teeth to complete chewing process.

18. Changes of cusps throughout evolutionc The earliest therian mammals (placentals and marsupials) had teeth with three cusps, arranged in a triangle, with the base running along the labial edge of tooth.  As our ancestors faced diet and habitat changes, structure Of our teeth have changed as well

19. conclusion From all of analyses and comparations we can come into conclusion, that our teeth are spotlight on our past and they are great tool to understand the changes our anthropoid ancestors faced and adaptations that they have made. Many studies have proved, that the changes that our teeth have faced, they are strongly inter-related to our muscular and cerebral development

20. Literature Goethe, J.W. 1963. Schnfen zur Botanik und Wissenschafslehre . 240 pp. Deutscher Taschenbuch Verlag. Miinchen . https:// royalsocietypublishing.org / doi /full/10.1098/rsbl.2015.0326 https://evrimagaci.org/20-yas-disleri-korelmis-organlar-ve-evrim-259 Marine Biological Laboratory Library Our Face from Fish to Man https://phys.org/news/2018-03-homo-naledi-wear-resistant-molars.html#nRlv Gidley, J.W. 1906. Evidence bearing on tooth-cusp development. Proceedings of the Washington Academy of Sciences 8. 9 1-1 10. Gingerich. P.D. 1976. Cranial anatomy and evolution of early Tertiary Plesiadapidae (Mammalia. Primates). University of Michigan. _ Museurn of Paleontology, Papers on Paleontology 15, 1- 141. Gingerich, P.D. &

21. Thanks for your attention