‘Thus life by life and love by love
Langdon Smith, American poet: Evolution’ (1895)
We passed through the cycles strange,
And breath by breath and death by death
We followed the chain of change.’
Evolution is a marvellous mystery. Well, it is a mystery if you are not deeply versed in evolutionary biology, and don’t know what cladograms and phylogenetic trees are. For those of us who haven’t devoted a lifetime of study to this – our – world, the best way of describing these diagrams is to call them ‘trees of life’, and they represent graphically how species have evolved and split over the eons. We have all probably seen them in books and articles, representing the growth and evolution of homo sapiens and other modern day creatures in the form of branching diagrams. Conceived and described by polymath Aristotle 2 346 years ago, the first example of these charts was developed back in 1840 by American geologist Edward Hitchcock in his ground breaking (literally) work Elementary Geology, describing geological relationships among plants and animals.
This work predated Charles Darwin’s 1859 On the Origin of Species, where he used a diagrammatic evolutionary ‘tree’ to illustrate his – at that time – revolutionary theory of evolution. In evolutionary biology, all life on Earth is theoretically part of a single phylogenetic tree, indicating common ancestry. The term phylogenetic, or phylogeny, derives from the two ancient Greek words φῦλον (phûlon), meaning ‘race or lineage’, and γένεσις (génesis), meaning ‘origin or source’.
If you are scratching your heads over just where this treatise on biodiversity is heading in an article from Waterfront Charters, a Cape Town V&A Waterfront cruise company, scratch no longer: it’s to do with pinnipeds. Still confused? Seals: those playful, carnivorous, predatory, fin-footed, semiaquatic intriguingly odiferous marine mammals that reside in numbers around our coastline on islands and in harbours. They are a delight to observe, whether they are just chilling on their platform near the Robben Island ferry terminal, or swarming around one of the many small atolls on our coastline; swimming and diving in graceful harmony. Our Cape Fur Seals are only one of the pinniped genus; there are 34 different members of the seal group, and these include the elephant seals, walruses, eared seals and sea lions as well as the ‘true seal’ or earless seal. Species of this latter group of seals live mostly in polar and subpolar regions, so are not commonly seen on the South African coast.
Seals vary enormously in size, too: from the 1m long and 45kg Baikal seal to the 5m and 3 200 kg southern elephant seal. As we know, all seals live an aquatic lifestyle, but do emerge from the ocean to breed, moult, rest or, like us humans at Clifton Beach, just to lie in the sun and think happy thoughts. Some seal species migrate, and the northern elephant seal is the Guiness Record Holder as far as this is concerned: a staggering 18 000 to 20 000 kilometres there (wherever that may be) and back to its Arctic home. It’s no wonder they lounge around in the sun occasionally.
But back to our phylogenetic tree and more head scratching. If we were to poll all the guests that board our eight vessels and ask them what creature was most closely related to our cheerful seals – all seals, in fact – it’s highly unlikely that any person would come up with an answer that came close to reality (unless, of course they were marine biologists). Ponder on the question a while before reading on for the answer…
If you said ‘penguin, whale, dolphin or porpoise’ – in fact any water based creature – you are wrong. If you were thinking laterally and said ‘even-toed ungulate’, like the whales and dolphins, you are also wrong. But if you said ‘skunk,’ you are either a marine biologist or very well-read, and correct. Come to think of it, if you had said ‘weasel, raccoon or red panda’ you’d have been pretty close to the mark too. Belonging to a major grouping known as Carnivora (flesh eating), the pinnipeds (finned-foot) closest relatives are the musteloids (weasel-like) of the suborder Caniformia (dog-like). Now you now. However, when one looks at pictures of the weasel, skunks and the seals, there actually is a resemblance, unlikely as it may seem. What we don’t see is the fact that their jaws and teeth share many similarities, and have probably evolved the least differences in fifty million years or so since the pinniped ancestors started spending more time in the ocean, probably after getting a taste for seafood. And who could blame them?
On Waterfront Charters cruises you are almost certain to encounter our own brand of pinnipeds lounging around or torpedoing through the ocean; they are always welcome sights for our guests and raise happy smiles and generate energetic photography. Join us: from Harbour Tours to Ocean Safaris, we offer wonderful views of sea life at its most vibrant, while you relax and take it all in.
And finally, if you are ever downwind of an island seal colony it will leave you in no doubt of their links with skunks. You will be an instant believer in phylogenetic trees.
