The Comparison of Molar Traits in Krapina Hominids and Contemporary Humans

Abstract

Svrha ovoga istraživanja bila je utvrditi morfološke značajke okluzalnih ploha trajnih molara u krapinskoga hominida (KH) te dobivene rezultate usporediti s nalazima današnje populacije koja je činila kontrolnu skupinu (KS). Klasifikacija značajki okluzalnih ploha molara određena je prema standardima za karakterizaciju morfoloških varijanti trajnih zuba po ASU (Arizona State University) - Dentoantropološki sustav Državnog sveučilišta u Arizoni). Ukupno je obrađeno 77 molara KH, od toga 34 gornja i 43 donja. U KS ukupno je obrađeno 4836 molara, od toga 2548 gornjih i 2288 donjih. Raščlambom okluzalnih ploha molara utvrđeno je : u trećih i drugih gornjih molara KS smanjenje čestoće distolingvalne kvržice; nestankom ili redukcijom veličine distolingvalne kvržice nastala je promjena obrisa okluzalne plohe iz romboidnog u trokutast, te gubitka H-sustava brazdi, koji je znatno češći nalaz u KH (p < 0,05). Na prvome gornjem molaru nađeno je najmanje razlika između dviju promatranih skupina. Samo po obilježju Carabellijevo svojstvo nađena je znatna razlika u zastupljenosti i to s većom čestoćom u KH (p < 0,01). U donjih molara (M1, M2, M3) KS utvrđena je smanjena čestoća distalne kvržice (p < 0,01). Na M3 i M2 u objema promatranim skupinama najzastupljeniji crtež brazdi je oblika +. Oblik X postoji samo u KS. Na M1 dominantan crtež brazdi u objema skupinama je oblika Y. Na osnovi navedenih rezultata može se zaključiti da je u današnjega čovjeka na molarima nastala redukcija broja kvržica i promjena oblika okluzalnih ploha, što je dovelo do smanjenja ukupne žvačne površine zuba. Kako je prema stajalištima antropologa crtež brazdi oblika Y najkonzervativniji, a oblik X najrazvijeniji, može se zaključiti da je M1 najkonzervativniji i da u evolutivnom smislu nije postignuo gotovo nikakav napredak. U M2 dominantan crtež brazdi je oblika +. Kako crtež brazdi oblika + predstavlja razvojni međuoblik i može se uzeti kao najviši evolutivni stadij oblika Y, tj. kao početak oblika X, taj zub glede evolutivnih procesa spada u prijelaznu razvojnu fazu. Oblik X na M2 nađen je samo u KS, što potvrđuje da je u evolutivnom smislu taj zub postignuo znatan napredak u odnosu prema KH. Dominantan crtež brazdi na M3 u objema skupinama je oblika +. Crtež brazdi X nije nađen ni na jednome M3 u KH, za razliku od KS gdje crtež brazdi X postoji u preko četvrtine zuba. Takav nalaz upućuje na zaključak da je od svih donjih molara KS u evolutivnom smislu M3 dosegnuo najvišu razvojnu razinu.The aim of this study was to investigate morphological characteristics of occlusal surfaces of permanent molars in Krapina hominid (KH) and to compare them with the findings in the modern population (control group, CG). ASU (Arizona State University Dentoanthropological System) standards for the characterization of morphological variants of permanent molars were used for classification of occlusal molar surface characteristics. A total number of 77 KH molars, among them 34 upper and 43 lower, as wel as 4836 CG molars, among them 2548 upper and 2288 lower ones was analysed. The analysis of occlusal molar surfaces revealed a lower incidence of distolingual cusps in CG third and second upper molars. The disappearance of reduction in size of distolingual cusp resulted in a change in occlusal surface contour from rhomboid to triangular and H-shaped grooves were lost; these characteristics were more grequently present in KH (p < 0.05). The least difference was found in the first upper molar; the only significant difference was the Carabelli trait, present significantlly more frequently in KH (p < 0.01). In lower KH molars (M1, M2, M3) the incidence of distal cusp was reduced (p < 0.01). In both study groups the most frequent groove shape in M3 and M2 was + shape. X-shape was seen only in CG. The predominanat groove shape in M1 was Y-shape in both study groups. Based on these results, it may be concluded that the number of cusps was reduced ond the shape of occlusal surface was changed in modern humans, leading to a reduction in the tital masticatory surface. Since Y-shape is considered most conservative and X-shape considered the most advanced by athropologist, we conclude that M1 remained the most conservative and did not undergo any progression in tooth evolution. The dominant groove shape in M2 was +shape. Since the +shaped groove is considered intermediate stage the highest evolutionary stage of Y-shape, i.e. the initial stage in X-shape formation, this tooth can be considered the transitional stage in tooth evolutionary development. X-shape was found only in CG, indicating the significant advancement in tooth evolutionary development in comparisom with KH. The dominant groove shape in M3 was +shape in both study groups. X-shape was not found in any of KH M3 in contrast to CG, where it was found in more than one fourth of teeth. This finding indicates that M3 reached the highest developmental stage among all lower molars in CG