Paleoanthropology, a branch of anthropology, is the examination of ancient primates. Even though most individuals conducting this inquiry are anthropologists, paleontologists (belonging to the field of geology) might also scrutinize fossils of primates. Examining fossil remains is the foremost technique employed by paleoanthropologists. Nevertheless, they progressively utilize other scientific areas to enhance comprehension of environmental elements that influenced our evolution and the creation of the fossil record. For instance, geologists ascertain sedimentary processes and fossil formation, and date fossils along with their accompanying sediments utilizing diverse methods (refer to DATING TECHNIQUES below). Multiple scientific domains partake in recreating prehistoric environments and biological communities. Paleontologists distinguish prehistoric floral and faunal fossils. Palynologists scrutinize particles in marine and lake cores, as well as pollen in earthly deposits (refer to Figure 1.2), to ascertain dominant flora in a region at certain periods. Taphonomists assist in determining the formation of fossil assemblages.
In the 1920s, Raymond Dart suggested that early bipedal primates (akin to ourselves) discovered in South African caverns were cave inhabitants. Furthermore, he deduced that perforations observed in some craniums indicated that these primates crafted and employed weaponry for hunting and combat between males. In later times, the taphonomist C. K. Brain advocated that hominins either plummeted into underground caverns after being stashed in trees by leopards, or their remains were hauled in by rodents, such as porcupines, for nibbling. It is now recognized that while early members of our line certainly utilized rudimentary utensils, they were neither avid big-game hunters nor combatants.
Chronicles of the Field
Albeit the formal acknowledgment of paleoanthropology as a scientific pursuit is relatively novel, the queries and doctrines connected to our inception can be traced back to the primary members of our species and conceivably even earlier. All modern humans residing in traditional (for example, hunter-gatherer assemblies, tribes, or chieftains) or state-level communities hold a set of notions associated with their genesis. Nevertheless, any proposition lying outside the province of science falls under a culture’s religious beliefs and are labelled creation narratives.
The most contributive disciplines to the emerging science of paleoanthropology have been geology, biology, and archaeology. Geologists (some unrecognized as such, e.g., Charles Darwin) are principally accountable for the acknowledgments that (1) the earth possesses an extensive history and was shaped through innate mechanisms; (2) water enveloped the planet originally, and life commenced in that primordial ocean; (3) the genesis of life on earth involved basal organisms, with some lineages evolving into intricate forms with time, as depicted in the fossil ledger; (4) organisms transform or vanish owing to environmental upheavals; (5) novel species arise when portions of the populace adapt to new or modified surroundings; (6) identical phenomena, such as volcanic eruptions, that are active presently are identical to those that have modelled the earth and lead to alterations in the fossil record due to extirpations and speciation episodes; and (7) strata and deposits are constantly forming or deteriorating so that lifeforms become entombed and fossils unearthed accordingly. The principle asserting that contemporary processes are parallel to those that sculpted the planet and instigated shifts in the fossil record is termed uniformitarianism.
Charles Lyell coined this concept and is celebrated as the progenitor of contemporary geology. His work profoundly influenced Darwin and thereby contributed to Darwin’s composite theory regarding the progression of life on this planet. Geologists deploy varied approaches to ascertain the age of fossils or sediment layers containing fossils and have established a chronology (i.e., a timeline) for the earth as an entirety, as well as for the deposition strata in locales where fossils have been located.
Biologists and geneticists have honed the philosophy of evolution via natural selection by elucidating trait inheritance. Authorities across various disciplinary fields have catalogued extant species based on evolutionary kinships.</f”>
Archaeology has, and continues to, perform a pivotal part in paleoanthropology via examining the archaeological record, meaning the remnants of former human comportment and anthropogenic (human instigated) environmental alterations. Thomas Jeffersonis often recognized as the inaugural archaeologist due to his systematic and scientific approach, unlike his antiquarian counterparts who pursued historical objects with little concern for the meticulous interpretation of archaeological finds. These antiquarians, by today’s definitions, might be classified as plunderers, removing items of immense cultural and historical value for either private enjoyment or for display in museums. Although some artifacts have been repatriated to their homelands, irreversible harm occurs once the archaeological context is disordered or devastated. When an object is extracted from its original setting, it strips researchers of the opportunity to study its relationship with neighboring finds or its placement within the broader spectrum of geography and chronology.
Significant contributions by archaeologists and geologists have been crucial in identifying “stones and bones” as traces of past hominin activities, with additional evidence from extinct fauna indicating the existence of humans across vast epochs. Techniques such as excavation and the study of provenance (that is, the exact three-dimensional position at a site) along with the relationship between artifacts (that is, transportable items fashioned or modified by humans) enable reconstruction of bygone behaviors. Similarly, taphonomy assists in interpreting both fossil and archaeological collections.
According to Merriam-Webster Online, the terminology “paleoanthropology” was first used in 1916. Nonetheless, those who initially engaged in this discipline had diverse backgrounds such as anatomists and physicians, and didn’t carry this specific title. The discovery of Neanderthals in the 1800s marked the first known hominin fossils, sparking debates about their relation to modern humans. The first deliberate hunt for a fossilized hominin was undertaken by Eugène Dubois, who journeyed to Asia aiming to corroborate the then-prevalent Western European hypothesis of human evolution originating there. In 1891, he uncovered both a skull cap (referred to as a calotte) and a femur along the Solo River in Trinil, Java.
Subsequent findings in Java and China throughout the early twentieth century lent credence to the theory of an Asian cradle for humankind until Raymond Dart and Robert Broom’s discoveries in South African sites questioned this belief. Later, the work of Louis and Mary Leakey in Eastern Africa established Africa as the cradle of humanity, igniting the quest to trace human ancestry.
Reconstructing Paleoenvironments
An assortment of methodologies facilitates the reconstruction of past species’ habitats. Paleontologists use both floristic and faunal assessment, drawing upon knowledge of ancient species or their living descendants, to infer environmental characteristics, including the existence of species in aquatic, savannah, or forested environments. Palynologists analyze microscopic particles present in aquatic and land strata, focusing chiefly on plant life. Isotopic tools play a crucial role in delineating plant and animal communities, with hydrogen, oxygen, carbon isotope fractionation, and nitrogen isotope ratios providing insightful data.
For instance, the analysis of isotopes in calcium-enriched remains like eggshells, bones, and teeth can indicate the types of plants consumed by animals, thereby deducing the nature of their habitats. One can ascertain diet composition by evaluating the ratio of strontium to calcium in bones and teeth. Using this technique, researchers have hypothesized that the paranthropines—early to middle Pleistocene hominins found in East and South Africa—ingested some animal matter. However, the details regarding whether their diet included insects or larger fauna remain unknown.
Dating Techniques
Dating methods can be categorized into relative and absolute. Relative dating techniques either (1) serially order strata through time or (2) infer the age of deposits in one region based on known deposits elsewhere, such as volcanic ash or lava layers. Jefferson is recognized for proposing the Law of Superposition, which suggests that unless disturbed by human, animal, or geologic activities, deeper strata are older, thereby providing a chronological context for artifacts or fossils embedded within these layers. Contrarily, absolute dating methods, also referred to as chronometric techniques, provide estimated dates in years BP (before present) or BCE (before the Common Era), both devoid of religious implications. To simplify timeframes, especially in the fossil record, researchers may employ abbreviations like kya or mya (thousands or millions of years ago, respectively), avoiding cumbersome zeros. BP is more practical since it does not necessitate adding over 2,000 years to the date to calculate the actual calendar year.The vast majority are familiar with the BC/AD dating scheme, which accounts for the widespread adoption of the Common Era (BCE). The most acknowledged methods for absolute dating are radiometric techniques, such as Carbon-14 (^14C). These methods are applied to measure the radioactive elements’ decay rate or renewal in ancient organic materials or the strata they occupy. Radiometric dating applications are subject to time constraints and environmental context, necessitating the selection of the most suitable method(s) based on diverse factors. Techniques employing radioactive decay for chronological determinations include:
Carbon-14 dating (up to 60,000 years ago) gauges the amount of ^14C residue in carbon-based materials. Plants incorporate atmospheric carbon dioxide, encompassing all carbon isotopes (^12C, ^13C, and ^14C) at ambient levels. Consequently, animals consuming these plants also maintain consistent ^14C levels. Post-mortem, carbon accrual ceases, enabling the comparison of ^12C stability to the diminishing ^14C to establish the time of death. The half-life of ^14C is around 5,700 years, signifying that half of the ^14C content dissipates over this duration.
Uranium series dating (up to 500,000 years ago) scrutinizes the concentrations of Uranium-234 and its decay product, Thorium-230. This method is especially useful for dating calcium carbonate found in coral and seashells.
Potassium-Argon (K/Ar) and Argon-Argon (Ar/Ar) dating both quantify the isotope ratio alteration through radioactive decay, specifically from Potassium-40 to Argon-40 and Argon-40 to Argon-39, respectively. Predominantly applicable to volcanic strata, they can also date other geological materials like clay. Notwithstanding the potential to date an extensive age range, K/Ar dating is less effective for recent materials due to the extensive half-life of Potassium, estimated at 1.26 billion years.
Additional methods reliant on radioactive decay encompass:
Electron spin resonance (ESR) (effective for a few million years) inspects electron dislocation in mineral matrices, such as calcium compounds, triggered by environmental radiation exposure. ESR is particularly reliable for dating tooth enamel within paleoanthropology and can be utilized for quartz sediment dating (Wagner 2006).
Fission track dating (20 million to 10,000 years ago) tracks the disintegration of Uranium-238 within mineral complexes, discernible as microscopic etching or tracks. A range of minerals, including mica, volcanic byproducts like obsidian, and extraterrestrial formations can be dated using this approach (Davis 2009; Wagner 2006).
Thermoluminescence (dating from 300 to 100,000 years ago) calculates radioactive particles within minerals, ideal for those subjected to intense heat such as during volcanic eruptions. This method resets the ‘radioactive clock’ to zero, allowing dating of ceramics, features like fire pits, sedimentation products such as cave formations (speleothems), and volcanic debris (tephra) (Davis 2009).
Dating methods divorced from radioactive decay and more dependent on biological processes are:
Dendrochronology leverages tree rings in ancient or charred timber to approximate the date of associated artifacts or fossils. Annually, trees add a new peripheral layer; wider layers form under favorable weather conditions. A cross-section narrates the tree’s growth history. For dendrochronology to determine ages, there needs to be a constructed chronology of the region’s yearly growth rates. Both extant trees and deceased timber can provide such data if their ring patterns correspond.
Amino acid racemization (ranging from 2 million years ago to 2,000 years ago ± 15%) deduces the proportion of two amino acid variants, one prevalent in living organisms and the other accumulating postmortem. Specimen dating is feasible if the temperature at the time of death can be estimated (Davis 2009).
Paleomagnetism (spanning hundreds of thousands to millions of years, Fagan 2000) deciphers historical alterations in Earth’s paleomagnetic fields recorded within specific ubiquitous minerals in rocks and sediments. Aligning these changes with established timelines enables approximate dating of material formation. Archaeomagnetic dating is the term when pieces of archaeological significance are dated with paleomagnetic evidence.
Obsidian hydration (100 to 1 million years ago) establishes dates for volcanic glass by measuring its elemental exposure-induced hydration. This process aids in dating obsidian objects and chronicling glacial and volcanic happenings (Davis 2009).
Surface or Cosmogenic Nuclide Exposure Dating quantifies the duration of rock exposure to environmental elements. It finds its application in glaciation events, lava flows, rockslide incidences, and impacts from outer space (Davis 2009; Wikipedia contributors 2015i).
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