In many ancient societies time was never considered a measurable unit. To them if time was measurable one should be able to hold a basket full of time -the basket being the unit for measurement known to them. Measuring tangible objects must have been there since the prehistoric period, but time being not tangible requires conceptualization.
In pre-literate societies one can often come across dating the age of an individual in reference to a memorable natural event. Ancient Egyptians and Babylonians are believed to be the earliest to attempt a calendar on the basis of astronomical and climatic events. Most of these calendars and their method of construction are today in semi-obscurity but these attempts can demonstrate man’s curiosity of calibrating the past into some comprehensible units.
The calendar is a product of our civilization which measures the past in such units as years, month and days. In dealing with prehistory such units are hopelessly useless and hence new units are required to be defined. The prehistoric units for the measurement of time are mainly in the form of a variety of climatic events of worldwide nature and hence these can never be as precise as our calendric units.
One of the most important involvements of most prehistorians, therefore, lies in reconstructing the past climates of a given area and then correlating this with a broad successional sequence of worldwide events in order to pin the new area within a specific stage of this sequence. There are a large number of scientists working in various natural science disciplines to obtain a calendar year estimate for these events or even to date given prehistoric objects.
The dates obtained through these allied agencies and expressed in units of years are termed as absolute or chronometric dates. It is needless to emphasize how wrong this term is, because all such estimates are very tentative and have a large range of plus-minus errors in many cases.
The rest of the approaches to dating give only indirect estimates called relative dates.
We shall briefly enter into all these dating techniques just for a basic awareness of the beginner, because in most cases these principles and actual working are very much outside the area of interest of average prehistorians:
1. Relative Dating:
One of the simplest approaches to chronology is based on the principle that the lowest layer in any natural process of deposition is older than the ones above it (provided there has been no disturbance). The youngest phenomenon under the same logic will be represented by the topmost layer.
The succession gets reversed if the depositional agency has the power of constantly getting lower in level through time. The classic example of this kind of stratigraphy is recorded in many river banks in the form terraces. Thus, in a terraced stratigraphy it is often the topmost layer, or more correctly terrace, which are the oldest and the lowest layer the youngest.
(b) Time Pleistocene:
The Pleistocene is an epoch which forms a part of the Quaternary period which in turn is a part of the Cenozoic Era. Various other divisions of the era and the periods contained within it are given in every book of palaeontology but do not concern us in prehistoric archaeology. The Pleistocene epoch is the epoch within which man evolved in the form of Australopithecus.
The beginning of this epoch is believed to lie anywhere between 5-4 million years from today and is defined in terms of the first appearance of some marker fossils. These are as a group called Villafranchian flora and fauna and include the ancestors of modern cow (Bos), elephant (Elephas) and horse (Equus) on land and Hyalinthica baltica in sea.
Most of the estimations done so far to fix the date for this event (viz., to mark the beginning of Pleistocene) indicate the Pleistocene epoch to have started around 5-4 million years ago and ended around 8,500 B.C. To every prehistorian this epoch is of extreme importance because just before its beginning Ramapithecus separated out to form a line of human evolution and throughout this period man passed through at least 4 broad evolutionary stages and a minimum of about 12 different cultural stages.
It is only after the Pleistocene ends that man starts domesticating plants and animals. Pleistocene epoch is marked by a rhythm of several glacial advances over Euro-Asia and the Americas. All these periods of glacial advances were not of equal intensity neither were the intervening warm periods of the same type. Some scientists believe that during the height of these glaciations compact ice of 2000 to 3000 mt. thickness stayed over the land for several hundred thousand years.
The enormous amount of water trapped in the land borne ice caused severe lowering of the sea level exposing land bridge between many islands and their adjoining main lands. In many favourable coasts these ancient beaches have been found and named corresponding to the Alpine glacial order.
The glaciations which descended down from the North Pole accompanied glaciers of all glaciated mountains gliding down to lower plains. In Europe the glaciers have been identified by giving them names of rivers on the Alps. There are several synonyms used for each of these names in different parts of Europe, Asia and Americas but to avoid complications we will use the Alpine names only.
The estimation of dates of 5 million to 500,000 years is done through a radio-active isotope disintegration technique known as Potassium- Argon method while dates upto 90,000 years are done by a similar method based on Carbon isotopes. The rest of the dates lying between 500,000 years to 90,000 years are done through relative dating techniques and hence are very tentative. Before we go into these methods of dating it will be important to understand how the glacial/interglacial chromometer is applied in practice.
A large number of plant types (described and defined through the identification of their pollens in soil) and animal types (described and defined through the identification of their skeletal remain in soils) specific to each of these climatic stages are established as a guideline. Any prehistoric site in which these indicators of environment are found associated along with the cultural debris, the dating becomes relatively easy by comparison of the latter with the established guideline.
In many cases, in spite of these faunal (animal) and floral (plant) availability a precise date may not be easy to arrive at because the faunal and the floral types found may be the ones which show no change of form for a relatively large part of Pleistocene. In other words, what is taken as archaeologically more fortunate is the availability of what is called the marker fossils. Marker fossils are those which are known to change into different species or sub-species at known periods within the Pleistocene.
Thus, insects, reptiles, fish or even some forms of mammals are quite useless in ascertaining the specific period within Pleistocene. Certain sub-types of elephants and rhinoceros have been found quite useful because they have changed into 3-4 different sub-species during this period. When such marker fossils are not available the archaeologist may try any method -from soil chemistry to methods of soil deposition – by air or rivers in order to link their find indirectly to one of the 7 broad stages.
The actual process of obtaining a chronological status for a given deposit is in reality an extremely long one. Recently experts in palaeomagnetic reversals recorded the actual size of reversal of the North Pole into South Pole. In the last 3 million years the north pole of the earth seems to have become South Pole 10 times and each of these reversals has been named and dated.
2. The Tropical Rivers and Lakes:
Almost all rivers and lakes in the world are getting narrower and shallower because of the tons of debris that they have accumulated during the past. A series of stable periods have caused down cutting of the bed and eventually changing the course. Deposits brought by the river in the past have sometimes been found more than a kilometer away from the modern flow of the river in a terraced structure.
Studies of these available terraces in African and Asian rivers demonstrate that tropical regions of the planet underwent an excessive rainfall period during the time glaciations were occurring in the temperate regions. During these heavy rainfall periods the rivers accumulated huge amount of debris which were eventually discharged when the water content dried up and could no longer carry them.
Thus, a series of boulders or gravels are found in stratified deposits along the banks of all ancient rivers and lakes. The periods of high rainfall are called pluviations and the dry periods between two pluviations are called inter-pluvials. There are 4 such pluvial deposits found in East Africa and these pluvials are termed as Kageran, Kamasian, Kanjeran and Gamblian.
Possibly these were occurring in the same general time period when Europe was recording the four glacials, i.e., Kageran during Gunz, Kamasian during Mindel, Kanjeran during Riss and Gamblian during Wurm. Some parts of Africa record two more wet phases after Pleistocene and these are named Makalian and Nakuran.
The evidences known till date seem to indicate that in India although there might have been as many wet phases as in Africa but most of the rivers were not born in the initial phases to record them. The earliest deposits recorded may not be older than the Kamasian in some rivers while in others it might have been even younger than this.
3. Fluorine Dating:
All bones and teeth are mainly composed of a phosphate named hydroxyapatite and the ground water in most places contains flourine. If therefore, a bone is lying buried in the ground, the fluorine from the water is absorbed by the bone to form a stable chemical compound called fluorapatite.
The amount of fluorapatite in a prehistoric sample of bones can, therefore, be taken to discard younger incorporations. Since many of the fossils of early man have been found washed up at the shore of water sources or simply on the surface, this method can atleast establish the relative antiquity of the finds.
4. Pollen Dating or Palynology:
Pollen is small grains released by different flowering plants. These have excellent preservative ability and are also different in structure for different genera or types of plants. Recovering the pollen from prehistoric soil can help reconstructing the plant life of the environment of that time.
Since plants are extremely sensitive to the climate their relative proportion through a depth of stratigraphy can sometimes reveal the process of slow change of environment during the period of soil deposition. The relative proportion of large trees or arboreal plants (AP) and grass and bushes or non-arboreal plants (NAP) has often been used as an index (AP/NAP X 100) to establish tundra from a thick forest in many stratigraphic profiles.
This is one of the most popular and useful methods of relative dating available for comparatively younger periods in Archaeology. Basically it involves identifying minor stylistic changes in a given type through a period of time. If the frequencies of people using a specific style in a given time are represented as horizontal bar and the frequencies of its use in successive periods are likewise arranged, then we observe the so called “battle ship” i.e., there are very few people who start using the style on its emergence and slowly its popularity increases (the middle of the ship) and finally again the popularity decreases.
If this series constructed for a given type has some absolute dates, then any surface collection within the area can be ascribed a date by comparing with this battleship design. Recently the method has been used with sophisticated statistics to attempt automatic arrangements of units into a series. Stylization in ceramics has been very successfully dated with this method.
6. Chronometric Dating:
This most widely used dating technique can be grouped as radio-isotopic methods, the theory of the most well-known of these, called radiocarbon technique, was first given in 1940. It is based on the fact that solar radiation striking the upper atmosphere converts a small amount of the atmospheric nitrogen into radioactive isotope-Carbon-14. Since all living organisms exchange gases with the atmosphere the amount of Carbon-14 in their cells soon reaches the same levels as in the environment.
When the organism dies the trapped Carbon-14 in the cells begin to disintegrate back as nitrogen. Laboratory experiments have established that half of any amount of Carbon-14 disintegrated in 5730 years (that is, its half-life is 5730 years). By measuring the amount of radioactive carbon left in a prehistoric organic remain one can calculate the time that has passed since its death. This method can give reliable date’s upto about 50,000 years after which the radioactive carbon left is too little to be measured.
Potassium-argon dating is based on the same principle but can be done only on rock or volcanic ash samples. It is because Potassium-40 is known to be constantly decaying into a gas called Argon-40. The half-life of this disintegration is about 1.3 million years. Since Argon is a gas, it escapes when the rock is molten like in lava but gets trapped when it cools. This trapped amount can be measured from volcanic deposits.
Most of our prehistoric sites cannot be dated by this method because they do not occur in volcanic ash and also because dates lesser than 500,000 years become unreliable. In other words, between 500,000 to 50,000 years i.e. the entire length of Middle Pleistocene and a considerable part of Upper Pleistocene are not datable through any radiometric method.
Dendrochronology is another chronometric method of dating which is of limited applicability. The cambium lying between the wood and the bark forms rings during yearly growth period of a tree. It is a common experience to see these rings in trees cut across the trunk. These concentric rings maintain minute differences of structure for each year depending on the temperature, humidity and age of the tree.
Certain trees, especially bristlecone pine (Pinus aristata) found in California has provided different ring structures for as many as 4,900 years. Each of these structures is plotted against their year of formation calculated from the outermost ring dated to the year of its cutting. Finally the prehistoric sample of unknown date is compared for its ring structures with the already identified structures.
This technique has been successfully used in dating many Palaeo-Indian habitation sites. For most of our prehistoric period this technique cannot be used simply because of lack of any surviving wooden sample. This technique has, however, played a very important role in correcting the earlier obtained radiocarbon dates.
It was found that the assumption that every living organism all through the past had maintained the same amount of Carbon-14 in their cells, as a present day living organism does, was not entirely correct. Hence many radiocarbon dates showed younger values for older (real) dates. With bristlecone pine dates radiocarbon dates have been corrected for 1000 to 4000 years. All radiocarbon dates are written as BP (Before Present) which by an international agreement is meant to be before AD 1950.
Varve analysis is another chronometric dating technique used successfully in obtaining the age of some prehistoric events. It is based on the principle that glacial lakes have an increased amount of water in the summer than in the winter and therefore the thickness of the fine clay deposition in the lake will be more in summers than in winters.
Physical counting of these darker varves or bands can lead one to estimate the age of the lake as also the time since its melting had started. This method has successfully demonstrated the exact time of the end of Pleistocene when the permanent ice covering most of Scandinavia started receding. Prehistoric sites are seldom found by glacial lakes and hence this method has no direct utility in prehistoric culture datings.
Fission Track dating is based on the principle that uranium atoms decay by emitting alpha particles which causes fission track damage on the surface of the material. Volcanic glass or some other minerals known to contain uranium show these damages under microscope.
If the total amount of uranium present in the sample and the density of the tracks can be counted the ratio between the two gives the age of the sample according to pre-determined constants for the rate of spontaneous decay. This method is still in its experimental stage and is applicable only on object having a glassy surface.
Many materials including clay and stones can store energy by trapping electrons from impurities. This energy is stored until the material is heated. On heating, this energy is emitted as a glow and this is termed as thermoluminescence or simply TL glow. On cooling, the alpha particles are again absorbed by the material.
The rate at which the energy is reabsorbed since last heating can be calculated in the laboratory. Thus, if a prehistoric ceramic sample can be energized to estimate the amount of alpha particles reabsorbed since it was last heated, the period elapsed since its last use can be computed.
Obsidian is black opaque glassy rock which is also referred to as natural or volcanic glass. This stone has been abundantly used during recent prehistoric past. Whenever a fresh obsidian nodule is fractured, water from the environment starts getting absorbed in the newly exposed regions and forms the band of obsidian hydration layer.
The rate of hydration formation can be determined in the laboratory under controlled conditions. The thickness of hydration layer found in prehistoric obsidian sample can then be converted into years by using the rate of hydration. This method is very easy and also cheap but can be used only on obsidian and hence is frightfully limited in its applicability.
Archaeomagnetic dating is another chronometric method of dating which is limited in its applicability to regions for which accurate data of earth’s magnetic field and angle of Dip etc. are recorded for last several hundred years. Since such data are not available beyond 1600 AD its applicability to prehistory is ruled out. For Palaeo-Indian habitation sites, however, it has been fruitfully utilized.
The technique is based on the principle that clay has impurities of ferric salts which are magnetic in nature. When a prehistoric fire hearth or kiln is heated its magnetic impurities develop earth’s magnetic field for that region for that period. If magnetic data for the region through time are available a mere comparison can show in which year it was fired.
7. Some Recently Developed Methods:
Human bones contain several amino acids. When polarized light is thrown on them some of these rotate the lights to the left while there are others which rotate the light to the right. The former types of amino acids are called 1 -isomers and the latter are called d-isomers. Most of the amino acids when found in living proteins are 1-amino acids but when the organism dies these slowly change to the right rotating or d-isomers.
This phenomenon is known as racemization. It was demonstrated that the racemization of a specific amino acid called aspartic acid, takes place in the period between 5000 to 100,000 years. Many prehistoric bones are now being subjected to the identification of d-isomers of aspartic acid in order to estimate the date. There are some successful dates also available from this technique.
Another method proposed is to estimate the rate of patina formation in a kind off rock called lydianite and through this estimate the date of prehistoric debris in which these stones are present.
There are many other dating possibilities which are being constantly investigated in various laboratories but these researches are completely outside the arena of archaeological research.
8. General Environment during Pleistocene:
It is true that the evidence of huge glaciers gliding over the land in Europe and America is demonstrative from the debris they have left behind, the effect of these ice sheets staying for sometimes, as long as 100,000 years, needs to be better understood.
It is believed that during at least the last two glaciations the climate of northern hemisphere was nearly four times colder than the present arctic region. Rocks and boulders pushed along the tip of the advancing glaciers made mounds along the tip of the limit where these glaciers stopped. Such deposits are called moraines. Moraines are studied by geologists to find out the path and extension of various past glacial episodes.
The annual temperature during the peak glacial periods went as far down as – 100°C while during much of the interglacials the temperature did not rise beyond 0°C – 10°C. During the stay of the ice the ground water was completely frozen (permafrost) and hence the water molten from the weight of ice could not get absorbed in the ground.
This created an expanse of slush around the lip of the morains. Advancing glaciers furrow through undulating land surface and in the process discharge a great deal of dust in the air. This dust is carried by strong wind currents created due to the cooling of surface air. This wind borne dust (called loess) is found deposited to great heights. These loess deposits often yield a very rich assemblage of faunal material.
During inter-glacials it is not only the sea level that rose by more than 100 metres but in many places the landmass also got raised because of the release of the tremendous weight of ice. These fluctuations had considerable effect on the vegetation zones of the area. Studies show that the timber line had been swinging back and forth by sometimes as much as 10 degrees of latitude.
In the tropical zones, effects of excessive rainfall are visible along the rivers and lakes but the environmental temperature was much lower than in winters today. As a result of this many of the plants and animals found in these zones seem to be tolerant in temperature fluctuations. Grassland and Savanna dominating the non-equatorial zones accommodated a large variety of animal types.
The interpluvial dryness accompanied the temperature rise and spread of grassland and desert almost to the periphery of the equatorial regions. Active pluviation had again changed these regions into thick rain forests. The various climatic zones identified today are described below with their environmental characteristics. For reconstructing prehistoric climate the understanding of the characteristics of these present day zones comes quite handy.
It is a vegetational condition which is negatively defined. That is, it refers to areas where no vegetation grows. There can be two different kinds of tundras, the one which is found in the Polar Regions and at high altitudes in the temperature zone, and the other in the deserts. Both are caused by lack of water in the soil. In cold tundra the soil water is frozen and hence cannot sustain any plant life while in deserts there is no useable water in the soil.
Discontinuous mosses, sedges or lichens in the polar tundras and shrubs of xerophytes in the desert tundras are the usually occurring vegetations. One can perceive several sub-zones of the Tundra on decreasing climatic severity. Such terms as HERBACEOUS TUNDRA or even TRANSITIONAL FOREST-TUNDRA are used to designate such shades or climatic variations.
It is a term used to designate grass-land environment. Seasonal moisture maintains very long grasses and other herbaceous plants over large stretches of land over the mid-latitudes, i.e., 30° to 40°M and 30° to 40°S. These occur in areas where winter temperature reaches very low limits for more than 4 months in a year, where exceptionally low temperature is maintained over a long period of time-as long as 4 months at a time.
The summer and spring precipitation is not enough to maintain arboreal (plant) life. As such, thick clods of grass with the network of their roots spreading far and wide come into their own. These roots are destroyed during winter and subsequently putrefied to provide nutrition for the growth of plants next spring. Steppe land can develop both in the periphery of the tropical forests as also in Tundra. Thus it forms a specific kind of gradation of both the extreme forms of vegetational regimes.
iii. Tropical Forest or Tropical Rain Forest:
This is a term used to designate an extreme form of vegetational regime. It constitutes a thick growth of hygrophytic, evergreen, and broad-leaved vegetation. Several layers of trees grew in succession with their canopies reaching in height many times the mark of 50 metres. The distance between the trees can also get reduced thereby, sometimes to as little as a meter.
Lianas and climbers occur in profusion where grass or any other kind of undergrowth is virtually absent. Normally this kind of vegetational zone occurs between 10° N to 10° S where humidity constantly remains above 90 percent all-round the year. In South-East Asia the Rain Forest extends almost upto 20°N.
Whenever this kind of forest develops a gap in its overhead canopy (because of the soil conditions below), sun light penetrates it right upto the ground and dense undergrowth takes birth. Regions where the rainfall is not uniform and comparatively drier summers occur, the rain forest starts growing deciduous vegetation and trees and soon a mixed forest results.
This is a term used to indicate a transition from a proper Rain Forest to a Steppe gradation. Grasslands interspersed with isolated trees of both the evergreen and the deciduous variety occurs in this kind of a climatic zone. This is a characteristic feature of the vegetation found all over the sub-humid tropics. Lighter tropophytic plants are a commonly found constituent of these forests.
This is also referred to as the Parkland phase in some countries. Usually regions maintaining rains continuously for more than 6 months in a year develop this form of ecology. It is believed that more and more of the Tropical Rain Forests of the world are fast metamorphosing into Savanna in their characteristics because of their overexploitation by man.
The identification of all stratigraphic units in a given deposit necessitates through investigation of the soil and its gradation. Frost weathering (cryoclastism), particularly evidenced in the soil sediments in caves and rock-shelters, and is indicated by laminated and angular chunks layed over soft soil.
Such deposits are often referred to as eboulis or talus in archaeological literature. Weathering of sediment during wet phase is identified from the amount of carbonate that is leached through the soil. The length and severity of the wet phase, naturally, can be attempted by quantitative chemical analysis of the soil.
A special kind of in situ weathering of rocks in the tropical countries called laterization, may be described at this juncture. This is a process by which the clay minerals of the rock are broken down during excessive rain thus enriching the weathered surface with minerals. These minerals are later crusted by a process of irreversible crystalization.
Laterites are rich in iron oxides and are brick red in colour. Forested rocks around the tropics are known to have lateritic deposits well over 10 meters in thickness. Seasonal rains wash these oxides of iron and deposit them along the lower valley drainages. Theses secondary deposits of laterites are called detritus laterites or simply detritus.
The agency which causes a soil deposition is identified through sedimentological studies. The deposits caused by permanent course of water flow (river) are called alluvial or fluvial deposits. The ones caused by lakes are called laccustrine deposits. The ones caused by wind are called aeolian deposits.
Finally those caused by advancing glacials are termed morains. The degree and duration of these agencies at a given place is often attempted through grading of the soil samples from these deposits. Various soil grading standards are being followed in various labs.
Here we may give an example from one standard:
Blocks – 10-10 mm in diameter
Granules – 10-5 mm in diameter
Gravels – 5-2 mm in diameter
Sand – 2-0.5 mm in diameter
Silt – 0.5 – 0.002 mm in diameter
Clay – 0.002 mm or less in diameter
If 100 gms of soil from any deposit is estimated for these gradations and expressed in percentages, any deposit caused by a forceful agency will tend to incorporate very high percentage by weight of the larger components while lesser the force the finer the particles will become.
Such sedimentological graphs, when drawn through time, can indicate how the climatic phenomenon controlling the agency has fluctuated in the past. These climatic fluctuations are then established by faunal and floral analysis. Hence an extreme dry and hot period between two extreme wet and humid periods can be easily diagnosed on the basis of sedimentology.
The temperature fluctuation if present for a long enough period of time can be more easily understood from the vegetable and animal remains. A combined interpretation of climate of a period through a multipronged analysis of a given deposition leads to defining stratigraphic units.
The changing climate of Pleistocene is also marked by changes in the fauna and flora in various parts of the world. While the flora has either to adapt to or perish with adverse changes in the climate, the fauna in many instances survived by migrating to regions of milder climatic stresses. In cases of long periods of climatic changes evidences of fauna also having adapted to the changed situation may not be entirely unknown.
Pollen-grains studies (Palynology) from deposits in north-west Europe show that early Pleistocene supported Azoila tegeliensis, Tsuga, Najas intermedia, Pterocarya limburgensis, Trapa natans and Coreva intermedia. These floral forms are usually referred to as Tiglian after the Tegelen clay in Limburg in Netherlands where they were identified.
The subsequent warmer phases see the evolution of Microtus and Mimomys. The Azolla feliculoides, Corylus and Abies are introduced successively. The last interglacial is marked by high proportion of hazel and horn bean in Europe. Betula pubesceus, Populus tremula, Pinus sylvestris and Alder are the other floral types that characterize this phase.
The identification of a flora involves the analysis of pollen or microscopic investigation of charcoal remains. Usually Palaebotanists are specially trained for this kind of work. The percentage of each genus and species of plant is computed from the total of the pollens in a given sample. Finally what is known as the “pollen spectrum” of the deposit is constructed. For ecological interpretations certain groups of the plant types are made, such as “hydrophailus” and “heliophilous” plants.
A high percentage of the former group will undoubtedly indicate a wet environment. A predominance of the heliophilous group of plants, on the other hand, will indicate sunny open spaces. Similarly, the proportion of arboreal plants (AP) to non-arboreal plants (NAP) in a given specimen can indicate a grassy steppe (high NAP) or forested environment (high AP) during the past periods.
The faunal finds from each of these periods help in fuller understanding of early man’s environment. The Villafranchian stage in Europe is marked by such large mammal forms as Elephas meridionalis, Dicerorhinus etruscus, Equus stenonnis and Trogentherium cuvieri.
Of these Elephas and Dicerorhinus show important evolutionary changes during the Pleistocene and thus act as two extremely helpful markers in archaeological datings. Elephas (Archidiskoden) meridionalis in Europe and Elphas. A planiforns in Asia are found till Cromerian faunal stage beginning from the early stages of the Villafranchian.
By the beginning of the Mindel glaciating these early elephants give rise to straight-tusked Elephas palaeoloxidon antiquus. These straight tusked elephants survived till Wurm. The Mammuthus trogontherii seems to be another variant evolved from the ancestral Elephas meridionalis. From an ancestral form of mammoth also developed the Elephas mammuthus primigenius. It is found in Riss and disappears in Wurm.
Similarly, Dicerorhinus megarhinus and Dicerorhinus etruscus of the Villafranchian stage are found to survive upto the middle of Mindel in Europe. It gives rise to the Dicerorhinus kirchbergensis (merckii) and D. hemiotechus in the subsequent period. These two forms continue to occur till the early phase of Wurm. During the height of Mindel glaciation the Woolly rhinoceros (Coelodonta tichorhinus antiquitatis) evolved somewhere outside Europe and migrated in every peak glacial phase.
Besides these large mammals European Upper Pleistocene witnessed the emergence of such forms as Megaceros giganteus, Hippopotamus amphibius major, Equus, Caballus silvestris, Ovibos maschatus, Felis leospelaeus, Rangifer tarandus, Bison priscus, Cervus elaphus and many other well-known modern animals.
Faunal and floral analysis can help to reconstruct past environments to a large extent. Certain animals can thrive in certain kinds of habitat. They also maintain symbiotic relationship with a set of other animals within the same habitat. Further, a certain kind of temperature, moisture and soil alone can provide the specific vegetation pattern for maintaining this animal population.
Most geochronological ascriptions are, therefore, entirely dependent on researches on these diverse branches of knowledge (geology, botany, zoology.) We not only measure time on the basis of establishing climatic succession but we also learn a great deal about past environments with which our ancestors interacted.