How Does Amber Preserve Ancient DNA and Fossils?
Fossil resin from trees that has achieved a stable state after the loss of volatile constituents and chemical change after being in the ground, is called amber. It has been appreciated for its natural beauty and colour for a very long time. Although it is primarily used in jewellery as amber gemstone, it also has several medicinal uses.
Amber Formation
Amber is produced by resin-bearing amber trees that thrive in a cluster in dense forests that have now become extinct. When coniferous trees are damaged, they give out a sticky substance called resin. It protects trees by sealing the gaps, breaks, or gashes in the bark, caused by chewing insects. As the resin flows on the surface of the tree, it hardens and forms a seal. Its antiseptic properties protected the tree from disease, and the stickiness gummed up the jaws of burrowing insects.
When this resin falls to the ground, it gets hardened in moist areas such as lagoons, riverbeds, and seabeds. This leads to the formation of amber material. Amber can be defined as fossilized resin that has been undisturbed for millions of years. Most of the world’s amber is at least 30 to 90 million years old.
The resin that became amber originally consisted of liquids (volatiles) such as acids, oils, and alcohols. It also contained aromatic compounds (terpenes) that cause amber’s distinctive resinous smell. Over years, the liquids evaporated from the resin, and it began to harden. The organic molecules merged to create larger ones called polymers. The hardened resin continued to polymerize and lose volatiles under the right conditions and eventually formed amber. Amber is an inert solid which has no volatiles when completely polymerized. The resins were buried in virtually oxygen-free sediments to transform into amber.
Appearance
Amber is available in a wide range of different colours and in the shape of irregular rods, or nodules. Sometimes it acquires the form of stalactites and drops, retaining the manner in which it exuded from the receptacles and ducts of the injured trees. Amber flows out onto the surface of the trees but sometimes in addition to that, it also flows into hollow cavities or cracks within trees, which leads to the formation of large lumps of irregular-shaped amber.
The most common and popular colour in amber is the usual yellow-orange-brown hue that gives it the name "amber". Yellow amber is a hard fossil resin derived from evergreen trees. Amber is also found in opaque or milky-white colour (also known as “bone amber”), pale lemon yellow, brown, and even an almost black colour. Other uncommon hues of amber include red amber (also known as "cherry amber"), green amber, and blue amber.
The presence of multiple minute air bubbles in the amber causes turbidity in it. Most of the time, varied species of fossil insects and plants are also found as inclusions in amber. Those in deep translucent hues and transparent amber are considered amber gemstones.
Amber Characteristics
Commonly, amber has a refractive index of 1.5–1.6, a hardness between 2.0 and 2.5 on the Mohs scale, gravity between 1.06 and 1.10, with a melting point of 250–300 °C.
Amber Mining
Amber was collected from along the shoreline of the Baltic Sea during the prehistoric era when it got deposited by large waves and strong tides. It was also gathered from lakes and rivers where it was deposited. In current times, open cast mining on the surface of the earth and in tunnels is the way most amber is mined.
Use of Amber in DNA Analysis
Amber plays a critical role in the DNA analysis of several prehistoric insects and animal species. As the tree resin fell on the surface of trees, sometimes insects and plants got trapped in this resin. Since amber is transparent, these trapped insects and plants are clearly visible even after the resin has fossilized into amber.
Many times, animals as large as frogs and lizards were trapped in the resin. As the bodies of these insects, animals, and plants are well preserved in amber, sometimes it is possible to extract their DNA. By studying the DNA of these trapped creatures and plants from prehistoric times, scientists have been able to learn a lot about those times.
FAQs on Amber: Formation, Features, and Biological Significance
1. What is amber and how is it formed?
Amber is not a stone but is fossilized tree resin that has hardened over millions of years. The formation process begins when resin seeps from ancient trees, often conifers. This sticky resin gets buried under layers of soil and sediment. Over millions of years, the immense pressure and heat cause the resin's molecules to polymerize, transforming it into the hard, translucent material we know as amber.
2. What is the scientific importance of amber in biology and palaeontology?
Amber's primary scientific importance lies in its ability to act as a natural time capsule. As the original tree resin was sticky, it often trapped small organisms like insects, spiders, pollen, feathers, and even tiny lizards. These are called inclusions. Because the resin hardened around them and protected them from decay, these organisms are preserved in stunning, three-dimensional detail. This provides palaeontologists and biologists with an invaluable, unaltered look at ancient life and ecosystems from millions of years ago.
3. What causes the different colours in amber, and why are some varieties so rare?
The colour of amber depends on several factors, including the type of tree it came from, its age, and what was trapped inside. Common colours are yellow, honey, and orange.
- Air Bubbles: Millions of tiny air bubbles can create a cloudy or opaque appearance (bony amber).
- Inclusions: Plant matter or minerals can cause greenish or darker hues.
- Heat and Oxidation: Over time, exposure can create a reddish 'cherry amber'.
Rare varieties like blue amber, found mainly in the Dominican Republic, are highly prized. Their unique blue or green glow under ultraviolet light is caused by fluorescent hydrocarbons from the extinct tree species Hymenaea protera, making this variety exceptionally scarce and valuable.
4. How can you distinguish genuine amber from common imitations like plastic?
There are several simple tests to distinguish real amber from fakes. Genuine amber has unique physical properties:
- Saltwater Test: Real amber has a low density and will float in a saturated salt solution (about 7-8 teaspoons of salt in a glass of water), whereas most plastics will sink.
- Electrostatic Charge: When rubbed vigorously with a soft cloth, real amber develops a static charge and can attract small pieces of paper or hair. Plastic does not do this as effectively.
- Scent Test: When a hot needle is touched to a discreet spot, genuine amber emits a distinct, pleasant pine or resinous scent. Fakes like plastic will release a harsh, chemical smell.
5. What are the common uses of amber, both historically and today?
Amber has been valued by humans for thousands of years for various purposes. Its main uses include:
- Jewellery and Ornaments: This is its most common use, crafted into beads, pendants, and other decorative items.
- Scientific Research: Amber with fossil inclusions is incredibly valuable to scientists studying evolution and ancient environments.
- Perfumes and Incense: When burned, amber releases a pleasant, woody aroma, and its oil is used in perfumery.
- Folk Medicine: Historically, it was ground into powders or worn as beads, believed to have healing properties.
6. What is the historical connection between amber and the concept of electricity?
The very word 'electricity' originates from amber. The ancient Greeks discovered that when amber was rubbed with fur, it gained an unusual property: it could attract light objects like feathers. They called amber 'elektron' (ἤλεκτρον). This phenomenon, now known as static electricity, was one of the first observed and recorded electrical effects in history. Thus, the study of amber's strange properties laid the foundation for our modern understanding of electricity.
