Rethinking Human Evolution

Y-DNA and mtDNA have been a widely used tool not only in forensic genetic applications but in human evolutionary and population genetic studies. Its paternal or maternal inheritance and lack of recombination have offered the opportunity to explore genealogical relationships among individuals and to study the frequency differences of paternal and maternal clades among human populations at continental and regional levels. It is unbelievable, but true, that the disadvantages of paternal and maternal lineages in forensic genetic studies, i.e., everyone within a family have the same paternal or maternal haplotype and haplogroup, become advantages in human evolutionary studies, i.e., reveal the genetic history of successful mothers and successful fathers. Thanks to these amazing properties of haploid markers, they provide tools for mapping the migration routes of human populations during prehistoric and historical periods, separately as maternal and paternal lineages, and together as the genetic history of a population.

An organism’s anatomy is the results of millions of years of interplay between DNA sequence, developmental processes, the environment, and evolutionary forces. The anatomical sciences are consequently highly integrative and interdisciplinary. That said, reaching across all of the relevant disciplines can be a daunting task because scientific publications are produced today at an astounding rate. This manuscript brings together insights from the quantitative genetic analysis of dental variation into the study of human evolutionary odontology within the context of genomics, genetic modularity, and phenomics. I primarily advocate for the use of quantitative genetics to not only identify QTLs, but also to assess the patterns of genetic covariance that underlie phenotypic covariance, thereby enabling us to conceptualize phenotypic variation as a reflection of the underlying genetic mechanisms. By highlighting three phenotypes of importance within the study of human evolution (patterning of the dental arcade, enamel thickness, and taurodontism), I demonstrate how an integrated consideration of quantitative genetics, genomic analyses, and paleontology can bring us to more detailed hypotheses about the evolution of the hominid clade.

ABSTRACTThe extended evolutionary synthesis (EES) is a school of thought that maintains that genetic determination and natural selection are over‐emphasized in the study of evolution at the expense of non‐genetic inheritance and processes of evolution beyond selection. Its proponents call for the de‐emphasis of genetics and the adoption of a broader model of inheritance that includes cultural and epigenetic transgenerational effects and strong adaptive phenotypic plasticity. Presenting itself as a radical alternative to what it claims is a rigid and ossified theoretical orthodoxy, the EES has lately gained considerable traction among scholars of human evolution, and a distinct sub‐branch of the EES unique to the biological anthropological study of human evolution has emerged (the EES in human evolution). To date, however, no direct comparison between the EES in human evolution and other contemporary evolutionary approaches has been attempted to evaluate whether the EES in human evolution affords researchers an edge in articulating good questions and structuring research programs to answer them. After reviewing the landscape of evolutionary theory, we evaluate whether the EES in human evolution is capable of delivering the processually pluralistic vision of evolution it has long promised and whether it brings something that the decades‐long ongoing synthesis (OS) of evolutionary theory since the modern synthesis does not. We then conduct a head‐to‐head comparison to evaluate the relative explanatory efficacy of the EES and our preferred OS theoretical framework on several issues of human morphological evolution. We demonstrate that evolutionary perspectives as drawn from the OS have a much more clarifying effect on the investigation of human evolution than their EES‐based competitor. Far from being a radical extension of evolutionary thought, the EES in human evolution offers little more than another idiom in which to tell adaptationist stories and triumphalist narratives of the ascent of humanity. Theory from the OS opens up new horizons of possible investigation of human evolution in a uniquely processually pluralistic and rigorous framework.

“Human Paleobiology” is about the use of fossils to determine the adaptations and evolutionary trajectories of human ancestors. At least part of this book’s purpose may be summed up in its title; this is Paleobiology, the study of long dead organisms via their fossils, as opposed to Paleoanthropology, the physical anthropology of dead people. Consequently, this book draws attention to the changes in studying the human past that are emerging within human evolution studies. Paleoanthropology has a history of being focused upon human ancestors, rather than the forces that shaped them. Arguments about phylogeny have tended to overshadow arguments about the causes and circumstances of evolutionary events. In fact, where evolution has figured at all, it has typically been about mechanisms that provide coherence to phylogenetic positions. Punctuated equilibrium provides support for multiple species of hominids. Post-synthesis population genetics can be viewed as providing support for a single genetically contiguous lineage. Various positions have held sway at various times. Loosely we can categorise these positions as the “lumpers”, those that folded various fossil finds into a single species, and the “splitters”, who were prepared to be a bit more generous with their taxonomic labels. Arguments about hominid phylogeny become particularly vigorous the closer to humans we get. The taxonomic status of Neandertals – ancestors or dead end – and the Modern Human Origins debate (MHO) provided some of the most spectacular fireworks. The lumpers see Homo erectus through to Homo sapiens as being “a single polytypic species” (Clark and Willermet 1997: 4). Currently in the ascendant are the splitters, or those that back

Cognitive Mapping and the Origin of Language and Mind

Morphology carries the primary signal of events in the evolutionary history of any group of organisms but has been relatively neglected by paleoanthropologists, those who study the history of the human species. Partly this is the result of historical influences, but it is also due to a rather fundamentalist adherence among paleoanthropologists to the tenets of the Neodarwinian Evolutionary Synthesis. The result has been a general paleoanthropological desire to project the species Homo sapiens back into the past as far and in as linear a manner as possible. However, it is clear that the human fossil record, like that of most other taxa, reveals a consistent pattern of systematic diversity--a diversity totally unreflected in the conventional minimalist interpretation of that record. Thus, the Neanderthals, both morphologically and behaviorally as distinctive a group of hominids as ever existed, are conventionally classified simply as a subspecies of our own species Homo sapiens--a classification that robs these extinct relatives of their evolutionary individuality. Only when we recognize the Neanderthals as a historically distinctive evolutionary entity, demanding understanding in its own terms, will we be able to do them proper justice. And we will only be able to do this by restoring morphology to its proper place of primacy in human evolutionary studies.

Tandem repeats in genomic sequences are characterized by two or more contiguous copies of a pattern of nucleotides. The role of these repeats as molecular markers is well established in various genetic disorders, human evolution studies, DNA forensics and intron retention. In this work a computational method has been developed for the extraction of both exact and approximate tandem repeats. The proposed algorithm uses Ramanujan Fourier Transform (RFT) to identify periodicities in the DNA sequences. Since RFT estimates the period directly, rather than inferring it from the signal's spectrum, it provides a more sensitive and rapid detection of tandem repeats as compared to other available popular computational methods.

Variations and asymmetries in regional brain surface in the genus Homo

Insights from Earth Sciences into Human Evolution studies: The example of prehistoric landscape use in Africa and the Levant

Analyses of molecular genetic data have added a new dimension to human evolutionary research. Pioneering studies of variation in human populations were based on analyses of blood groups1 and electromorphs,2 both of which represent qualitative multistate phenotypes. With the development of recombinant DNA methods in the 1970s and 1980s, the focus shifted from gene products to a new and plentiful source of human variability, restriction fragment length polymorphisms (RFLPs).3,4 Finally, the addition of DNA sequencining survey data to the rapidly growing RFLP data base made it feasible for the first time to determine the exact number of nucleotide substitutions between different alleles, as well as to construct gene trees and reconstruct the phylogenetic history of populations.5–7

Nancy M. Tanner was an ethnographer who, with her colleague Adrienne Zihlman, argued in the 1970s and early 1980s for the centrality of females in shaping distinctive traits emergent in hominin evolution. Tanner and Zihlman proposed that greater parental investment by female early hominins under changing environmental conditions could have led to technological innovation, as well as to female sexual selection as a force shaping male hominin behavioral traits. They also proposed that long‐lived matrifocal groups among early hominins could have been the locus of kin selection for increased provisioning of young by mothers and older siblings. Given the era's male‐centered scenarios for the emergence of distinctively hominin behaviors, Tanner's work was among the first to argue for a view of selective pressures operating on both sexes. Tanner's work presaged a turn toward greater attention to female social behavior and life histories in biological anthropology and human evolutionary studies.

The role of allometry and posture in the evolution of the hominin subaxial cervical spine

Analysis of DNA polymorphic sites is an important tool for the detection of gene flow in human evolutionary studies and to study the genetic background for gene mutations. The β-globin locus contains several single-base restriction fragment length polymorphism (RFLP) sites throughout chromosome 11. In addition to these polymorphic sequence repeats, others are being studied in order to expand our knowledge concerning the role between haplotype-genotype and phenotype associations. Far downstream of the expressed β-globin genes, there is a hypersensitive site (HS) whose function remains obscure. We sequenced this region in 27 thalassemia patients and found a new pattern in the micro-satellite-like AT-rich region of this site: a new TAA insertion in addition to the one previously described in sickle cell patients with a concomitant polymorphism (G→A). This new variation was found to be linked to the IVS-I-6 (T→C) mutation. This polymorphism may be useful for studies concerning genotype and phenotype associations.

The cis-regulatory element contributed to gaining humanness is of great interest in human evolutionary studies. A human-accelerated region exceeding neutral evolutionary rates, termed HACNS1, was recently reported as a positively selected sequence acquiring novel TF-binding sites responsible for human-specific gain of limb enhancer function. However, another possibility is loss of function in repressor element in HACNS1. Signature of the human substitutions in the 81-bp region infers that a GC-biased gene conversion (BGC) might create these seemingly excessive substitutions. To evaluate the 81-bp function, we performed transgenic mouse assay of the HACNS1 construct lacking the 81-bp region. The deleted construct showed similar enhancer activity to the intact human HACNS1, suggesting that the function of the human 81-bp region is not an activating enhancer but rather a disrupted repressor. This result infers that loss of function in the HACNS1 81-bp region, possibly via a BGC, played an important role in human-specific evolution.

A variety of geometric morphometric methods have recently been used to describe dental shape variation in human evolutionary studies. However, the applicability of these methods is limited when teeth are worn or are difficult to orient accurately. Here we show that elliptical best fits on outlines of dental tissues below the crown provide basic size- and orientation-free shape descriptors. Using the dm(2) and M(3) as examples, we demonstrate that these descriptors can be used for taxonomic purposes, such as distinguishing between Neanderthal and recent modern human teeth. We propose that this approach can be a useful alternative to existing methodology.