Tooth microstructure tracks the pace of human life-history evolution

Abstract

A number of fundamental milestones define the pace at which animals develop, mature, reproduce and age. These include the length of gestation, the age at weaning and at sexual maturity, the number of offspring produced over a lifetime and the length of life itself. Because a time-scale for dental development can be retrieved from the internal structure of teeth and many of these life-history variables tend to be highly correlated, we can discover more than might be imagined about fossil primates and more, in particular, about fossil hominids and our own evolutionary history. Some insights into the evolutionary processes underlying changes in dental development are emerging from a better understanding of the mechanisms controlling enamel and dentine formation. Our own 18-20-year period of growth and development probably evolved quite recently after ca 17 million years of a more ape-like life-history profile.

Imitation, pretend play, and childhood: Essential elements in the evolution of human culture?

“…Superimposed on this daily rhythm is a coarser, more prominent marking called the striae of Retzius that when viewed in crosssection appear as concentric rings, much like annual rings on a tree. Counting the striae enables evaluation of a specimen's age of death, thereby permitting dental eruption sequences to be calibrated against an absolute time scale (Dean, 2006). This means that the period of maturation in fossil primates can be reconstructed and compared in real time with living primates.…”

Retrieving chronological age from dental remains of early fossil hominins to reconstruct human growth in the past

“…Interestingly, all predictions so far for M1 emergence in fossil apes (Kelley 1997(Kelley , 2002Kelley & Smith 2003;Dean 2006) actually fall below the simulated median age of attainment for M1 emergence predicted in figure 3 as indeed do most estimates for early hominins. This raises questions about how different great ape dental development in the Late Miocene might have been to that known today for modern P. troglodytes and how good a model modern Pan is for comparisons with the earliest hominins.…”

“…The slope of these incremental markings, with respect to the junction between enamel and dentine, provides a way of estimating past rates of differentiation of new secretory cells during tooth formation (Boyde 1963(Boyde , 1964(Boyde , 1990bShellis 1984;Dean 1985;Risnes 1986). The rate of increase in both tooth crown height and root height can be reconstructed by dividing increments of tooth crown length along the enamel dentine junction (EDJ), or cement dentine junction (CDJ) by the time intervals taken to form them (Boyde 1963;Risnes 1986;Dean 2006Dean , 2009. In figure 2, consecutive 200 mm-thick increments of enamel and dentine have been used to plot increasing tooth height against time from the dentine horn to a point as close to completion of the root as possible (Dean 2009).…”

A Life Course Perspective on Health Trajectories and Transitions

“…The microstructure of enamel therefore provides a fascinating record not only of the timing of tooth development, but also of any disturbances due to early life experiences. These features of enamel are used also in anthropological and evolutionary research (Dean 2006;Humphrey et al 2008). Dental hard tissues can also provide important information on exposure to environmental pollution.…”