|Route of the Scotia
With regard to these developmental facts the question arises:— Is the duck's or the penguin's wing the more direct descendant of the common ancestor; or have they both diverged from the common stock approximately equally, but in opposite directions. Embryology alone cannot answer this question, but the evidence is clear in this, that the fore limb of the penguin in its development goes through a progressive and continuous series of stages along one unbroken line. The mesoblastic portion of the fore limb elongates, but its characters do not alter. It elongates, however, with a relatively greater rapidity towards the end of development, whereas the duck's fore limb, after being relatively longer than the penguin's ever is, regresses rapidly. So that the answer to our question, so far as the embryological evidence is concerned, must be that the wings of both these birds are different from the ancestral wing, and that the differentiation has been in opposite directions and that the common ancestor was a flying bird of a somewhat primitive type depending in large measure for the spread of its wing upon bone and muscle.
|One of the two laboratories on Scotia
|Coats Land. The expedition named this part of the
continent for the Coats family, the sewing cotton
manufacturers (now the multinational Coats plc),
who funded the expedition.
What is this venture? Why is the embryo of the Emperor penguin so important to Science? And why should three sane and common-sense explorers be sledging away on a winter's night to a Cape which has only been visited before in daylight, and then with very great difficulty?The Emperor is a bird which cannot fly, lives on fish and never steps on land even to breed. It lays its eggs on the bare ice during the winter and carries out the whole process of incubation on the sea-ice, resting the egg upon its feet, pressed closely to the lower abdomen. But it is because the Emperor is probably the most primitive bird in existence that the working out of his embryology is so important. The embryo shows remains of the development of an animal in former ages and former states; it recapitulates its former lives. The embryo of an Emperor may prove the missing link between birds and the reptiles from which birds have sprung*.After the deaths of Scott, Wilson, Bowers, Oates and Edgar Evans on their return from the Pole, Cherry-Garrard obtained a series of embryos from Adélie Penguins at Cape Royde. He wrote:
It was always Wilson's idea that embryology was the next job of a vertebral zoologist down south. I have already explained that the penguin is an interesting link in the evolutionary chain, and the object of getting this embryo is to find out where the penguins come in. Whether or no they are more primitive than other nonflying birds, such as the apteryx, the ostrich, the rhea and the moa, which last is only just extinct, is an open question. But wingless birds are still hanging on to the promontories of the southern continents, where there is less rivalry than in the highly populated land areas of the north. It may be that penguins are descended from ancestors who lived in the northern hemisphere in a winged condition (even now you may sometimes see them try to fly), and that they have been driven towards the south.
If penguins are primitive, it is rational to infer that the most primitive penguin is farthest south. These are the two Antarcticists, the Emperor and the Adélie. The latter appears to be the more numerous and successful of the two, and for this reason we are inclined to search among the Emperors as being among the most primitive penguins, if not the most primitive of birds now living: hence the Winter Journey. I was glad to get, in addition, this series of Adélie penguins' embryos, feeling somewhat like a giant who had wandered on to the wrong planet, and who was distinctly in the way of its true inhabitants.