![Australopithecus africanus - Cast of taung child](https://upload.wikimedia.org/wikipedia/commons/b/be/Australopithecus_africanus_-_Cast_of_taung_child.jpg)
An endocast is the internal cast of a hollow object, often referring to the
cranial vault
The cranial vault is the space in the skull within the neurocranium, occupied by the brain.
Development
In humans, the cranial vault is imperfectly composed in newborns, to allow the large human head to pass through the birth canal. During bir ...
in the study of brain development in humans and other organisms.
Endocasts can be artificially made for examining the properties of a hollow, inaccessible space, or they may occur naturally through
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
ization.
Cranial endocasts
Artificial casts
Endocasts of the inside of the
neurocranium
In human anatomy, the neurocranium, also known as the braincase, brainpan, or brain-pan is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calvaria (skull), ...
(braincase) are often made in
paleoanthropology
Paleoanthropology or paleo-anthropology is a branch of paleontology and anthropology which seeks to understand the early development of anatomically modern humans, a process known as hominization, through the reconstruction of evolutionary kinship ...
to study brain structures and hemispheric specialization in extinct
human ancestors
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, an ...
. While an endocast can not directly reveal brain structure,
[ it can allow scientists to gauge the size of areas of the brain situated close to the surface, notably Wernicke's and ]Broca's area
Broca's area, or the Broca area (, also , ), is a region in the frontal lobe of the dominant Cerebral hemisphere, hemisphere, usually the left, of the Human brain, brain with functions linked to speech production.
Language processing in the brai ...
s, responsible for interpreting and producing speech
Speech is a human vocal communication using language. Each language uses Phonetics, phonetic combinations of vowel and consonant sounds that form the sound of its words (that is, all English words sound different from all French words, even if ...
.
Traditionally, the casting material is some form of rubber
Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...
or rubber-like material. The openings to the brain cavity, except for the ''foramen magnum
The foramen magnum ( la, great hole) is a large, oval-shaped opening in the occipital bone of the skull. It is one of the several oval or circular openings (foramina) in the base of the skull. The spinal cord, an extension of the medulla oblon ...
'', are closed, and the liquid rubber is slushed around in the empty cranial vault and then left to set. The resulting hollow sphere can then be drained of air like a balloon and pulled out through the ''foramen magnum''. Rubber endocasts like these were the standard practice until the end of the 20th century and are still used in some fields. However, scientists are increasingly utilizing computerized tomography
A computed tomography scan (CT scan; formerly called computed axial tomography scan or CAT scan) is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers ...
scanning technology to create digital endocasts in order to avoid risking damage to valuable specimens.
Natural endocasts
Natural cranial endocasts are also known. The famous Taung Child
The Taung Child (or Taung Baby) is the fossilised skull of a young ''Australopithecus africanus''. It was discovered in 1924 by quarrymen working for the Northern Lime Company in Taung, South Africa. Raymond Dart described it as a new species ...
, the first ''Australopithecus
''Australopithecus'' (, ; ) is a genus of early hominins that existed in Africa during the Late Pliocene and Early Pleistocene. The genus ''Homo'' (which includes modern humans) emerged within ''Australopithecus'', as sister to e.g. ''Australopi ...
'' found, consists of a natural endocast connected to the facial portion of the skull. It was the shape of the brain that allowed Raymond Dart
Raymond Arthur Dart (4 February 1893 – 22 November 1988) was an Australian anatomist and anthropologist, best known for his involvement in the 1924 discovery of the first fossil ever found of ''Australopithecus africanus'', an extinct homi ...
to conclude that the fossil was that of a human relative rather than an extinct ape
Apes (collectively Hominoidea ) are a clade of Old World simians native to sub-Saharan Africa and Southeast Asia (though they were more widespread in Africa, most of Asia, and as well as Europe in prehistory), which together with its siste ...
.
Mammal endocasts are particularly useful, as they resemble the fresh brain with the dura mater
In neuroanatomy, dura mater is a thick membrane made of dense irregular connective tissue that surrounds the brain and spinal cord. It is the outermost of the three layers of membrane called the meninges that protect the central nervous system. ...
in place. Such "fossil brains" are known from several hundred different mammal species.[ More than a hundred natural casts of the cranial vault of '']Bathygenys
''Bathygenys'' is an extinct genus of oreodont of the family Merycoidodontidae, endemic to North America. It lived during the Early Oligocene 33.9—33.3 Annum, mya. Fossils are widespread through the western United States.
''Bathygenys'' was a ...
'' (a small merycodont) alone are known, some having identifiable features down to the major gyri
In neuroanatomy, a gyrus (pl. gyri) is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci (depressions or furrows; sg. ''sulcus''). Gyri and sulci create the folded appearance of the brain in humans and other ma ...
. Several hundred casts of various dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
s are known, among them a ''Tyrannosaurus
''Tyrannosaurus'' is a genus of large theropoda, theropod dinosaur. The species ''Tyrannosaurus rex'' (''rex'' meaning "king" in Latin), often called ''T. rex'' or colloquially ''T-Rex'', is one of the best represented theropods. ''Tyrannosa ...
'' brain vault, showing the animal had limited intelligence and a well-developed sense of smell. The oldest known natural cranial endocast is a fossil fish brain from a Holocephalan
Holocephali ("complete heads"), sometimes given the term Euchondrocephali, is a subclass of cartilaginous fish in the class Chondrichthyes. The earliest fossils are of teeth and come from the Devonian period. Little is known about these primit ...
, some 300 million years old.
Endocasts of other hollows
Endocast fossils from animals with shells that easily disintegrate or dissolve can often be encountered free from their mold fossil, like the aragonite
Aragonite is a carbonate mineral, one of the three most common naturally occurring crystal forms of calcium carbonate, (the other forms being the minerals calcite and vaterite). It is formed by biological and physical processes, including prec ...
shells of certain mollusc
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...
s and the tests of sea urchin
Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) of ...
s. A frequently occurring form is the internal mold of brachiopod
Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, w ...
s and bivalves
Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...
. In the quite symmetrical genus brachiopod ''Pentamerus
:''The gall mite genus ''Pentamerus'', established by Roivainen in 1951, is invalid and needs to be renamed. Until this happens, use '' Pentamerus (mite)''.''
''Pentamerus'' (meaning "five thighs") is a prehistoric genus of brachiopods that live ...
'', the endocast resembles a vulva
The vulva (plural: vulvas or vulvae; derived from Latin for wrapper or covering) consists of the external sex organ, female sex organs. The vulva includes the mons pubis (or mons veneris), labia majora, labia minora, clitoris, bulb of vestibu ...
, giving these fossils the name ''Schamstein'' or ''Mutterstein'' ("shame stone" or "mother stone") in German
German(s) may refer to:
* Germany (of or related to)
**Germania (historical use)
* Germans, citizens of Germany, people of German ancestry, or native speakers of the German language
** For citizens of Germany, see also German nationality law
**Ger ...
, while some bivalve endocasts are traditionally known as heart-of-stone or bull hearts in Britain. The "Venus of Svinesund", an early Mesolithic
The Mesolithic (Greek: μέσος, ''mesos'' 'middle' + λίθος, ''lithos'' 'stone') or Middle Stone Age is the Old World archaeological period between the Upper Paleolithic and the Neolithic. The term Epipaleolithic is often used synonymous ...
Venus figurine
A Venus figurine is any Upper Palaeolithic statuette portraying a woman, usually carved in the round.Fagan, Brian M., Beck, Charlotte, "Venus Figurines", ''The Oxford Companion to Archaeology'', 1996, Oxford University Press, pp. 740–741 Mos ...
from Norway
Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...
, is a re-worked Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...
bivalve endocast. Endocasts are also known to develop from snail shells and sea urchins, and even from the stomach hollow of jellyfish
Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella- ...
, a group that rarely leaves fossil traces.
Artificial endocasts are sometimes made from blood vessels for medical or anatomical reasons. The blood vessel of an organ (e.g. brain
A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...
or liver
The liver is a major Organ (anatomy), organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of proteins and biochemicals necessary for ...
) is injected with a resin
In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on natu ...
. When it is set, the organ itself is dissolved, leaving a three-dimensional image of the blood supply to the organ.
References
{{Reflist
Anatomy
Biological anthropology
Anthropometry
Animal anatomy
Fossilization