BY

Rakesh H

Research Scholar

Department of Biotechnology

Sahyadri Science College, Shivamogga.

KUVEMPU UNIVERSITY

E-mail-rocky.devrath@gmail.com

1. How we evolved from ape-like ancestors to modernhumans, including, when did we diverge from apes,who were the early hominids, and when did modernhumans spread out of Africa?

2. What makes us human - what are some of theadaptations that evolved as humans migrated aroundthe globe and established new cultures? In what waysare we still evolving?

In 1871 Charles Darwin proposed in his book “TheDescent of Man” that humans evolved in Africa andshared a common ancestor with great apes. Thisshowed remarkable foresight as at that time there wereno early human fossils and no DNA evidence.

In the case of human evolution, Charles Darwin noted that

humans and apes share many biological features .

He hypothesized that humans and apes share a common ancestor.

If this hypothesis is true then humans and apes should share a highpercentage of their DNA,

and there should be fossils with humans and ape-like features.

Darwin wasn’t able to gather this sort of evidence to test his hypothesisin his time, but many studies since then have tested these predictions .

Both DNA and fossil evidence support the hypothesis of humans and apes sharing a common ancestor, and the idea that humans evolved from ape-like creatures is now an accepted theory.

Who is more closely related to who?

The hominoids are descendants of a common ancestor.

Louis Leakey examining skulls

First fossils: the 1920s when such fossils were discovered in Africa, that intermediate species began to accumulate. In 1925, Raymond Dart described Australopithecus africanus.

The earliest human-like fossilshave been found in Africa anddate back to 4-8 million yearsago.

One of the most importanthominid fossils ever discoveredis that of “Lucy”.

Lucy was discovered by DonaldJohansson in Hadar, Ethiopia.

Lucy belongs to the species Australopithecus afarensis, and lived 3.2 million years ago.

She stood around 1.1 metres (3.5 feet) tall and she walked upright on two legs, although

she probably had a less graceful gait than us, since she walked with her legs bent.

humans belong to a group of mammals calledprimates

our closest living relative is the chimpanzee, ourevolutionary paths separated 5-7 million years ago

the human fossil record is quite good and reveals howand when ‘human traits’ evolved

modern humans evolved in Africa and migratedaround the world

DNA evidence supports these conclusions and isbeginning to reveal changes in genes important tohuman evolution

Mesopotamia Egypt Indus River China Mesoamerica Andes hunter-gatherers:

Southern Africa Australia / New Guinea Northern / Western Europe North Asia

[See tables: Earliest Domestication of Animals/Plants]

Begins….

ARCHAEOLOGY: The branch of anthropology thatstudies prehistoric peoples and their cultures throughtheir material remains.

MOLECULAR ARCHAEOLOGY: “Moleculararchaeology is, basically, the study of ancientmolecules. Archaeological studies which include thestudy of ancient molecules include DNA recoveredfrom human skeletal remains and the mummifiedbodies of humans

Proteins

Lipids

Carbohydrates

Nucleic acids

Proteins play structural and functional roles in livingorganisms.

Structural proteins, such as collagen and osteocalcin, which arefound in all vertebrate bones, are relatively stable and can oftenbe identified in preserved material.

Other proteins, usually ones that are less stable, have morelimited distributions. Casein, for example, is found only in milk,and can therefore be used as a marker for the presence of milkresidues in cooking or storage vessels. By showing that certainvessels once contained milk products, the development ofdairying in prehistory can be followed .

The blood protein, hemoglobin, has a slightly different structurein different species, and with modern material these differencescan be used to identify the origin of a bloodstain.

Lipids are a diverse group of macromolecules,

the major biochemical classes being fatty acids and their derivatives (whichinclude substances commonly referred to as fats and oils), waxes, steroids, andterpenes.

These compounds have various biological functions, both structural (somefatty acids are important components of cell membranes) and functional(some lipids are hormones).

Lipids are so hugely diverse that many are species specific – they are found onlyin a single or small group of species and so can be used as markers for thosespecies.

Analysis of lipids in organic residues from cooking vessels can thereforeidentify the type of vegetable or meat that was being prepared, and similarstudies with storage vessels can show if they were used to hold, for example, aparticular type of oil .

Identification of the terpenes in the adhesives used to attach flint arrow headsto wooden shafts can reveal which trees were exploited as sources of tar andpitch, taking biomolecular archaeology into the area of prehistoric technology .

Carbohydrates are important structural and storagecompounds in living organisms, and include starchand cellulose in plants, and glycogen in animals.

carbohydrates are the least studied by biomoleculararchaeologists because, although they are stable overlong periods, it is difficult to obtain useful informationfrom them.

One exception is the examination of starch grains inarchaeological deposits, which can indicate the typesof plants that were present at a particular site .

Two types, deoxyribonucleic acid (DNA) and , ribonucleic acid (RNA).

Three features of DNA make this molecule valuable in biomoleculararchaeology.

First, in the cell, DNA acts a store of biological information, whichmeans that DNA can be used to identify at least some of the biologicalcharacteristics of an archaeological specimen, such as the sex of ahuman skeleton .

Second, the DNA of different species can be distinguished, enablingDNA from a pathogen such as Mycobacterium tuberculosis to bedetected in human bones .

Third, DNA is a record of ancestry, and so can be used to deduce if twohuman skeletons could be related , and to map the evolutionaryrelationships between domesticated animals and their wild progenitors.

RNA molecules are copies of parts of the cell’sDNA, and could, theoretically, be used in a similarway to DNA, but RNA has not been extensivelystudied in biomolecular archaeology. This isbecause RNA molecules are relatively unstable,and it has been assumed (perhaps incorrectly) thatRNA is rarely present in human, animal or plantremains.

one human genome differs from the other, the evolutionary past that gave rise to it, and its current effects.

Differences between genomes have anthropological, medical and forensic implications and applications.

Genetic data can provide important insight into human evolution.

In the late 1980s that ancient DNA is sometimes preserved in humanbones that marks the true beginning of biomolecular archaeology .

DNA is the genetic material of living cells,

DNA contains a vast amount of information that, if accessed inpreserved specimens, could be of immense value in addressingarchaeological questions

the discovery of ancient DNA in archaeological specimens was madepossible by the invention of the polymerase chain reaction (PCR)

Extraction and purification of ancient DNA fromarchaeological remains.

The polymerase chain reaction is the key toancient DNA research.

Examining the sequences of cloned PCRProducts.

New methods for high throughput DNAsequencing.

a two-stage process,

the first stage involving extraction of all the solublemolecules from the specimen and

the second resulting in purification of the DNAmolecules from this mixture.

. DNA is readily soluble and can be extracted frommost materials simply by resuspending a ground orpulverized sample in water or a weak buffer.

After leaving the suspension for an hour or so to allowthe soluble component to leach out, the preparation isbriefly centrifuged so that the remains of the sampleare discarded as a pellet at the bottom of the centrifugetube, with the dissolved biomolecules retained in thesupernatant.

ancient DNA is contained in crystalline deposits within thebone matrix, which are not accessed when the bone isground into a powder.

Soaking the bone powder in a chelating agent such asEDTA, which removes calcium ions .

the main constituents other than DNA are protein andRNA.

The traditional way to remove these contaminants andhence purify the DNA is to add phenol or a 1 : 1 mixture ofphenol and chloroform,

as these organic solvents precipitate proteins and sometypes of RNA but leave the DNA in solution.

Any remaining protein and RNA can be digested bytreatment with protease and ribonuclease enzymes

FOSSIL BONES

PCR products obtained from ancient DNA should becloned prior to sequencing .

The central feature of a cloning experiment is thevector, a DNA molecule, often based on a naturallyoccurring plasmid, that is able to replicate inside a cellof the bacterium Escherichia coli.

DNA typing

BIO-editing

Representing different mitochondrial DNA haplotypes

Primer library

Unknown sequence- Blast ,Databases.

THIRD generation

The objective of an ancient DNA project is to understandthe evolutionary relationship between an archaeologicalspecimen and modern organisms.

The tree comprises a set of external nodes, eachrepresenting one of the sequences that has been compared

each representing one of the sequences that has beencompared, linked by branches to internal nodesrepresenting ancestral sequences.

. The lengths of the branches indicate the degrees ofdifference between the sequences represented by thenodes.

the main differences between them being the way in whichthe multiple alignment of the sequences is converted intonumerical data that can be analyzed mathematically inorder to produce the tree.

Phylogenetic Tree

The origins of modern humans.

DNA analysis has challenged the multiregional hypothesis.

DNA analysis shows that Neanderthals are not the ancestors of modern Europeans.

DNA can also be used to study prehistoric human Migrations.

Using mitochondrial DNA to study past human migrations into Europe.

Studying Disease in the Past.

END