Ancient DNA and Neanderthals DNA (deoxyribonucleic acid) is…

Ancient DNA and Neanderthals
DNA (deoxyribonucleic acid) is arguably one of the most useful tools that scientists can use to understand living organisms. Our genetic code can tell us a lot about who we are, where come from, and even what diseases we may be predisposed to contracting and acquiring. When studying evolution, DNA is especially important in its application to identifying and separating organisms into species. However, DNA is a fragile molecule, and it degrades over time. For most fossil species, there is essentially no hope of ever acquiring DNA from their fossils, so answers to questions about their appearance, physiology, population structure, and more may never be fully answerable. For more recently extinct species scientists have, and continue to, extract ancient DNA (aDNA) which they use to reconstruct the genome of long-gone ancestors and relatives. One such species is Neanderthals, Homo neanderthalensis.
Neanderthals were the first species of fossil hominins discovered and have secured their place in our collective imagination ever since. The first Neanderthal fossils were found in Engis, Belgium in 1829, but not identified as belonging to Neanderthals until almost 100 years later. The first fossils to be called Neanderthals were found in 1856 in Germany, at a site in the Neander Valley (where Neanderthals get their name from). Neanderthals diverged from modern humans around 500,000 years ago, likely evolving outside of Africa. Most ancestors of Homo sapiens remained in Africa until around 100,000 years ago when modern humans began migrating outwards. In that time, Neanderthals evolved many unique adaptations that helped them survive in cold environments of Europe and Asia. Their short limbs and torso help conserved heat, and their wide noses helped warm and humidify air as they breathed it in. Despite these differences, modern humans and Neanderthals are very closely related and looked similar. We even overlapped with each other-living in the same place at roughly the same time in both the Middle East and Europe. If this is the case, why did Neanderthals go extinct while we survived? We can use DNA to help to answer this question and others, including:
- What was the relationship between Neanderthals and anatomically modern humans?
- Did Neanderthals and modern humans interbreed? If so, where and to what degree?
- Did Neanderthals contribute to the modern human genome? How much?
- What do the Neanderthal genes in the human genome actually do?
- Are there any other species like Neanderthals that we have DNA evidence for?
Scientists answer these questions by comparing genomes as whole, as well as specific genes, between humans and Neanderthals. Before getting into the specifics of Neanderthal DNA, it is important to appreciate the structure of DNA itself, why it is so important, and why aDNA can be so difficult to work with.
Fast Facts
Fast Facts
- DNA degrades over time, so is only available for recently extinct species
- Neanderthals and modern humans shared habitats in Europe, Asia, and the Middle East
- We can study Neanderthal and modern human DNA to see if they interbred
DNA: The Language of Life
DNA structure and function
You may recognize the basic structure of DNA: two strands arranged in a double-helix pattern with individual bases forming rungs, like a twisting ladder. These bases are adenine (A), thymine (T), guanine (G), and cytosine (C). They form complementary pairs on opposite ends of each ladder rung: adenine across from thymine and cytosine across from guanine. For example, if one side of the twisting ladder reads AATG, the opposing side will read TTAC. It is the sequence of these individual base pairs that makes up our genetic code, or our genome. Errors can occur when DNA is unwound to be replicated with one or more bases being deleted, substituted for others, or newly added. Such errors are called mutations and range from being essentially harmless to deadly.
The main function of DNA is to control the production, timing, and quantity of proteins produced by each cell. This process is called protein synthesis and comes in two main stages: transcription and translation. When the cell needs to produce a protein, an enzyme called RNA polymerase ‘unzips’ the DNA double-helix and aids in pairing RNA (ribonucleic acid, a molecule related to DNA) bases to the complementary DNA sequence. This first step is called transcription, the product of which is a single-sided strand of RNA that exits the cell nucleus. This messenger RNA, or mRNA, goes into the cell’s cytoplasm to locate an organelle called a ribosome where the genetic information in the mRNA can be translated into a protein. The process of translation involves another kind of RNA, transfer RNA or tRNA, binding to the base sequences on the mRNA. tRNA is carrying amino acids, molecules that will make up the final protein, binding in sequence to create an amino acid chain. This amino acid chain will then twist and fold int…