Note: This series of posts is intended as a basic introduction to the science of evolution for non-specialists. You can see the introduction to this series here. In this post we introduce the development of languages over time as an analogy for speciation, and use this analogy to explore the challenge of finding a biological “beginning” of our species.
Anothir day Joon say Jhesu comynge to hym, and he seide, Lo! the lomb of God; lo! he that doith awei the synnes of the world. (Wycliffe Bible, 1395)
The nexte daye Iohn sawe Iesus commyge vnto him and sayde: beholde the lambe of God which taketh awaye the synne of the worlde. (Tyndale New Testament, 1525)
The next day Iohn seeth Iesus coming vnto him, and saith, Behold the Lambe of God, which taketh away the sinne of the world. (KJV, 1611)
The next day John seeth Jesus coming unto him, and saith, Behold the Lamb of God, which taketh away the sin of the world. (KJV, Cambridge Edition)
The next day John saw Jesus coming toward him and said, “Look, the Lamb of God, who takes away the sin of the world!” (NIV, 2011)
In previous posts in this series, we’ve outlined the challenge of finding a definitive biological “beginning” for a species, since declaring a “speciation” event is attempting to draw a line on a gradient of continuous change. A similar challenge besets linguists: though it is possible to divide the development of the modern English language into stages such as “Old English”, “Middle English” and “Modern English” such conventions are ones of scholarly convenience. In reality, the development of English is a continuum where speakers in each generation are perfectly conversant with both their parents and their children – and yet changes creep in that gradually shift the language over time. This is easily illustrated through the various texts of John 1:29 above: West Saxon (an Old English dialect in use in the late 10th century) is pretty much incomprehensible to modern readers, and cannot be adequately represented using a modern keyboard (hence the image). Four hundred years later (Wycliffe) and the text is significantly more readable, but comprehension is still a stretch. And on it goes: in the Tyndale version, things are increasingly more familiar, except for the equivalences of “I” and “J” or “v” and “u”, plus the extra “e” appended to several words – the latter of which is familiar to those who have read Shakespeare or the original 1611 edition of the King James Bible (KJV). The Cambridge edition of the KJV is quite familiar to many Christians, though it can hardly be said to be written in entirely “modern” English (despite being a prime example of an early Modern English text). Last but not least, the 2011 edition of the New International Version (NIV) reads easily for us, as we would expect a modern translation to do.
Language evolution is in fact one of the better analogies for biological evolution, in that it forces one to think of change in the context of a population over time. Just as a language has a population of speakers, so too a species has a population of genomes. Each member of a language group may have their own slight preferences of grammar, spelling, and pronunciation, just as a biological population will have genetic variation. Language variation within a population can also shift over time, as differences start and “propagate” by becoming more common, or others become less common and are eventually lost. One example seen in the verses above concerns the letters “u” and “v” in English – they were once entirely interchangeable – duplicates if you will. These duplicates later became distinct, however – they took on non-overlapping functions (sounds). The process by which this took place was a gradual one – the variation was there in 1611, but by the time of the Cambridge Edition(s) of the KJV (from the 1700s and following) their roles had stabilized to the functions we know. In addition to gains, loss of variation also can occur in languages (as well as in genetics, as we have seen). For example, Old English had an additional letter, thorn, which was gradually replaced by th in Middle English. (You can see three thorns in the West Saxon text above – it looks like a stylized “p” to modern eyes).
Language evolution as an analogy for biological evolution also helps us understand transfer of variation between languages (or, in the case of biological evolution, between species). English, as it is well known, “borrows” many words from other distinct languages, most notably from French. This borrowed vocabulary that was introduced into, and subsequently took root in, the English speaking population is analogous to genetic exchange between related species – populations of organisms that are distinct, yet not distinct enough to prevent interbreeding (and thus genetic exchange). This feature of language evolution also makes defining a “start” of a language problematic – since some of its variation is developed slowly within the population, and some is brought in from a related language (and thus reflects its prior history in the donor language). For species, variation from cross-species genetic exchange produces the analogous pattern, where some of the variation of a species has its history in another species altogether.
Languages and species: lines on a gradient
Having sketched out the analogy between languages and species, consider this question: when, exactly, did “English” have its origin? In A.D. 990 with the West Saxon text of John 1:29? No, for even in A.D. 990 the words of this verse have a deeper history into even more ancient forms of Old English. The question is in fact a meaningless one: there is no “first speaker” of “English”, but rather a population of speakers who gradually, generation by generation, have come to speak the language we call “Modern English.” Along the way, we can trace these populations and see the gradual shifts in their vocabulary, grammar, spelling, and pronunciation – changes that are quite dramatic when viewed over long timescales – but nonetheless accumulated bit by bit over time, without any breaks in continuity for the population. Each generation has a fully functional language, and each generation between A.D. 990 and the present day spoke the “same language” as the generation preceding and following them. Despite that continuity, however, one would be hard pressed to claim that West Saxon and present-day English are the “same language”: too much change has accumulated. The challenge, of course, is where to draw the line – and the exact same issue is what presents a challenge for biologists defining species as distinct. Widely-separated groups are easily distinguished when the variation connecting them has disappeared. If we had knowledge of West Saxon, and knowledge of present-day English, but nothing in between, it would be easy to classify these languages as distinct. Once one knows the history, however, such a distinction is revealed to be a line of convenience on what is in fact a continuous gradient.
As we have seen in previous posts, at the time of Darwin, the gap between humans and living great apes was viewed as very wide – as wide as West Saxon and modern English. Over time, however, other hominin species were found that – like texts preserved from different eras – suggest a continuous population undergoing gradual change. And as we will explore in the next post in this series, the analogy of “texts” for ancient species has become even more appropriate, for now we are able to recover and sequence DNA from ever more ancient hominin remains. Like a linguist uncovering long-lost manuscripts, these results give us a clearer picture of our origins – and indicate that our speciation was prolonged and complex.