Homo habilis - fiftieth anniversary

Homo habilis the handy man (Wikimedia Commons)

An article in the current issue of Nature (here) reminded me that 50 years have passed since Louis Leakey, Phillip Tobias and John Napier published their controversial paper, "A new species of the genus Homo from Olduvai Gorge" (here). Until then most fossil hominins had been accomodated in the genera Australopithecus and Pithecanthropus. Whether or not the new fossils justified the title of Leakey's paper was disputed then and remains contentious.

As I wrote at the time, "There are two criteria that might be used to define man: his ability to make tools and the size of his brain. Homo habilis scores on the first point but not on the second" (Carter AM. A new ancestor for man. The Humanist 1964; 79: 198-201).

Happy Birthday Jane Goodall

I was reading anthropology while the paper was being written and was taught by both Phillip Tobias and John Napier. I also met Louis Leakey on one of his visits to Cambridge - probably angling for a job - and was introduced to his protégée, the then unknown Jane Goodall (whose 80th birthday is today).

Anna-Riitta Fuchs

Anna-Riitta Fuchs (1926-2014)

Anna-Riitta Fuchs was a reproductive endocrinologist whose great interest was the control of parturition. Much of her work centred on the posterior pituitary hormone oxytocin and its receptors in the myometrium.

I first met Anna-Riitta and her husband Fritz at their laboratory in Copenhagen shortly before they relocated to New York. I was a very green graduate student back then but was received with great warmth as they patiently explained their work on parturition in the rabbit. Those were heady times when a great debate was raging about the most important determinant of birth: was it oxytocin release or the withdrawal of progesterone from the placenta?

Anna-Riitta's many achievements include a D.Sc. from the University of Copenhagen and the Carl G. Hartman Award from the Society for the Study of Reproduction. Anna-Riitta was born 1926 in Helsinki and died last week in New York. A full obituary can be found here.

Endogenous retroviruses expressed by ovine trophoblast

Urial Sheep (Ovis vignei)
Wikimedia Commons

Jaagsiekte sheep retrovirus (JSRV) is a nasty pathogen causing lung tumours in sheep. No fewer than 27 JSRV-related endogenous retroviruses (enJSRVs) occur in domestic breeds. Gene capture is an ongoing process and the distribution of enJSRVs has been exploited to test hypotheses about the domestication of sheep (here). For example, the most common variant (enJSRV-18) is absent in ancestral breeds such as the Urial (above) and Mouflon. Although found in goats, enJSRVs are not present in cattle so are much younger than a syncytin recently described by Cornelis et al. for ruminants (here).

Five enJSRVs are capable of transcription and like syncytins (previous post) they have an env gene. Are they then "nascent syncytins" as suggested by Cornelis et al., or do they already subserve a function in the ovine placenta?

A period of blastocyst elongation precedes implantation in sheep and binucleated trophoblast cells first appear then. enJSRV mRNAs are detectable at this stage and later are expressed in binucleate trophoblast cells as well as in the syncytial plaques formed by fusion of those cells with uterine epithelial cells (reviewed here).

Moreover, when antisense oligonucleotides were used to block enJSRV protein production, differentiation of binucleate cells was inhibited (here). The more i read about endogenous retroviruses the more intrigued I become.

Blood supply to brain and placenta in the capybara

Capybara (Hydrochoeris hydrochaeris)
Wikimedia Commons

The current issue of Science (here) draws attention to recent work on the blood supply to the brain in capybaras. As in other mammals young capybaras have a dual supply from the internal carotid arteries and the basilar artery. At one year of age, however, remodelling of the internal carotid shuts down that source and the basilar artery becomes the sole source of blood to the brain. Research on the underlying mechanisms is being conducted at the Department of Surgery at the Veterinary School in Sao Paulo (here).

The Department is also home to a vibrant research group led by Angelica Miglino with whom it has been my privilege to collaborate on the blood supply to the capybara placenta (here and here).

Placentation in the capybara from Kanashiro et al.
Reprod Biol Endocrinol 2009 (here)

Like other hystricognath rodents, capybaras have a discoid, labyrinthine, haemochorial placenta with an inverted yolk sac that persists to term. An additional feature shared with other hystricognaths is the subplacenta (sub in panel D above). With Claudia Kanashiro we published a detailed study of this structure in the capybara (here). 

It is encouraging to see Science advocate the capybara as a model for stroke. In view of its size - at around 65 kg it is the largest living rodent - it might be useful as a model for fetal physiology. As shown in a previous post on the guinea pig, hystricognaths have precocial young and are in this respect more satisfactory models for gestation than mice and their kin. 

Ten thousand birds

Birkhead, Wimpenny and Montgomerie
Princeton University Press 2014 ISBN 978-0-691-15197-7

Because a bird has no placenta, Eggs is how this world they enter (Simon Drew). Yet it would be remiss of me not to mention this lucidly written and lavishly illustrated narrative of the history and philosophy of ornithology.

The opening chapter, "Yesterday's Birds," is a fascinating account of the progression of ideas on the origin of birds, including the influence of the Danish artist and self taught palaeontologist Gerhard Heilmann, who surmised birds evolved from thecodonts (Pseudosuchia). The alternative view of birds as dinosaurs (BAD), promoted in the 1970's, was slow to take hold. A related story concerns the origin of feathers, which were long thought to be highly modified scales but now are seen as a novel evolutionary development. The chapter brings us up to date with feathered but flightless dinosaurs, including superb fossils from China, the colours of fossil feathers and the different type of keratin that distinguish scales from feathers.

One word of caution: despite the title this is not an overview of the various families of birds although it does contain many paintings and photographs to delight the eye of the amateur ornithologist (a group not recognized by the authors to whom ornithologists are scientists and the rest mere bird watchers).

Trophoblast Research

A new issue of Trophoblast Research has just appeared. Entitled "Models for Molecular Understanding of Placental Development and Associated Disorders," it reports the proceedings of IFPA Meeting 2013 at Whistler, British Columbia.

There are 15 review articles and three comprehensive workshop reports all open access. To view them go to the Placenta web site and scroll down until you find the above image in the left side bar.

Disclosure: I am Editor of Trophoblast Research.

Tempers ran hot over tarsiers

Philippine tarsier (Tarsius syrichta)
Jasper Greek Golangco

A recent post dealt with controversy over the evolution of placentals. This is nothing new. In 1897 debate ranged in the pages of Science about whether tarsiers belonged with lemuroid or anthropoid primates. It was sparked by the work of Hubrecht, who claimed that the embryological development of tarsiers resembled that of higher primates. He pointed to the precocious development of the extraembryonic mesoderm as well as the absence of an allantoic sac and its replacement by the connecting stalk.

Skull of Anaptomorphous

Had he stopped there all might have gone well. But Hubrecht proceeded to give a new interpretation of the primate fossil record, in particular Anaptomorphous homunculus (now placed in Omomyidae). This raised the ire of Charles Earle, curator of fossils at the American Museum of Natural History. He argued on the basis of osteological characters and dentition that tarsiers might represent an intermediate stage between lemuroids and anthropoids but certainly did not belong with the latter (here). In a spirited reply (here), Hubrecht wrote, "It is, indeed, rather hard upon me...to be now pilloried by Mr. Earle as if I had been making that coarse and indiscriminate use of placentary characters in classification against which I have been all the time loudly protesting."

In the next exchange (here), Earle argued for the superiority of palaeontological over embryological methods in determining phylogeny. He rather spoiled the effect by presaging one argument, "On this side of the Atlantic..."

As a footnote it is worth observing that there remain huge gaps in the fossil record of primates and the position of Anaptomorphous is still open to alternative interpretations. Meanwhile Hubrecht's view has triumphed over Earle's with primates split in Strepsirrhini (the lemuroids) and Haplorrhini (tarsiers and anthropoid primates).