zoo:logic

In an extraordinary biological study, researchers have used chemical analysis to demonstrate that ink preserved in the remains of two cephalopod fossils that date over 160 million years ago to the Jurassic period is almost identical to that used by modern common cuttlefish (Sepia officinalis) today. The cephalopod fossils were found at sites in Christian Malford, Wiltshire (162 million years old) and Lyme Regis, Dorset (195 million years old) in the UK and included preserved three-dimensional ink sacs. Biological tissues rarely survive in fossilised material as they are almost always quickly degraded by microorganisms. But some types of organic substances found in living organisms may last for long periods of time if they are polymeric - large and made up of multiple subunits - and have a tough cross-linked structure. One such substance is melanin, of which the form eumelanin - which takes a dark black or brown colour - is known to be a key chemical component of modern common cuttlefish ink.  Cephalopods use the dark-coloured ink to reduce visibility when threatened so they can rapidly escape without being caught. Mucus is also sometimes added to the ink allowing it to hold a form for a limited period of time, giving the illusion of ‘false bodies’ that act to distract predators from the real organism. Eumelanin remains were found to be well preserved in the ancient fossilised ink sacs through a number of different chemical tests. The maintenance of ink chemical composition over this huge period of time suggests that the use of ink as an anti-predator strategy has retained its evolutionary benefit for well over 160 million years and is fully optimised for its purpose.

Ref: Glass K. et al., 2012. Direct chemical evidence for eumelanin pigment from the Jurassic period. PNAS Online before print [link]

For a long time, the history of the domestication of the horse has been a muddled one. While archaeological evidence suggests that the domestic horse (Equus caballus) originated in the western Eurasian steppes (Ukraine, southwest Russia and west Kazakhstan), a large variety of female lineages in the gene pool contradicts this, implying not a single origin but instead multiple domestication events. An important unanswered question was whether the spread of horse domestication around the world involved the actual movement of herds from a specific geographic origin, known as ‘demic spread’, or whether it simply involved passing on successful techniques so that people in other regions could domesticate their own local wild horses, resulting in multiple domestication events from numerous different populations. New research that has analysed mitochondrial DNA and Y-chromosomes from a genetic database of over 300 horses has finally resolved the answers to these questions. The data has traced the origins of domestic horses to a single ancestral population of Equus ferus (now extinct) that was indeed living in the western Eurasian steppes from at least 160,000 years ago. Humans first domesticated the horse in this region around 4000 B.C., and from here domesticated horses spread outwards across Europe and Asia, in the process of which stock was supplemented with local wild horses in different regions. These wild horses that were bred into domestic herds were the source of the new female lineages that we can identify in the gene pool today.

Ref: Warmuth V., Eriksson A., Bower M. A., Barker G., Barrett E. et al., 2012. Reconstructing the origin and spread of horse domestication in the Eurasian steppe. PNAS Online [link]