The road from Darwin's theory of natural selection to the Francis-Crick DNA structure was a long one indeed, one that took more than a 100 years to traverse. Although most scientists, including Darwin himself, had a hunch that there was an hereditary substance that passed on characters through generations, it was only in the 1950s that this was narrowed down to the deoxyribonucleic acid (DNA) of the chromosome. Once the mystery of the DNA, its structure and its role in passing on information, started to get unraveled, biological thought became extremely gene-centered. That adaptation could occur only through natural selection of chance genetic variations became the biologist's mantra. However, recent advances in molecular biology are causing a gradual change in our concepts of heredity, genes and evolution.

For the last two decades, Eva Jablonka and Marion Lamb have been trying to understand the manner in which biological systems operate and transmit information through generations. In Evolution in Four Dimensions, they lay out some startling conceptual theories that are changing the way in which we view heredity and evolution. What Jablonka and Lamb posit is that, in addition to genetic systems in evolution (i.e. information passed through the DNA), other non-DNA inheritance modalities such as those based on epigenetic, behavioral and symbolic (language and culture-based) forms also exist. Together these four provide all the variations within which natural selection acts and evolution proceeds. In other words, these pathways intersect and form a tangled web through which the transmittal of biological information occurs.

Examples of the epigenetic systems are specialized cells, such as cells from the liver, heart, or kidney of an individual that, despite possessing the same genetic information, are completely different. This is possible because of the "information" introduced at a developmental phase (usually embryogenesis, or the period of embroyonic development) that tells them which genes need to be turned off or on. Interestingly, these cells can transmit this information of their specialization to their daughter cells.

A highly recommended read for lovers of genetics and evolutionary biology, Evolution…, though formidable looking as all works on evolution usually are, is in fact quite the opposite. Credit goes to the authors, who have tackled this comparatively difficult topic with ease using numerous illustrations and examples from day to day life. They are, however, on slippery ground with the last two hereditary systems, namely behavioral and symbolic, at least at far as biologists are concerned. Jablonka and Lamb argue that if two sets of populations have different lifestyles, then it is possible that over thousands of years they would evolve differently; that is to say that their behavioral patterns may be significantly diverse. Could a new invention and its social diseemination possess the potential to alter an organism's long-term behavior en masse? Examples in the animal world are very few and far between.

Again, the role that symbolic inheritance, the fourth hereditary system, plays in evolution of a species is somewhat controversial. Symbolic implies the transmittal of information by acquiring and organizing knowledge and by thinking and communication through symbols such as language. The bank of acquired information ensures that every successive human generation does not have to reinvent the wheel. But the million-dollar question is whether or not symbolic transmittal can add a developmental dimension to a species: a dimension that functions irrespective of the environment.