Professor Adolf Portmann (27.V.1897 Basel – 28.VI.1982), Swiss zoologist and anthropologist. Former Rector of University of Basel.
His name is listed among fifteen “great names, great achievements” of Basel University next to Paracelsus, Bernoulli or Nietzsche (1). He is sometimes considered to be one of the most original biological thinkers of the twentieth century (2)(3). Recently there has been a revival of interest in his work (2)(3)(4). His books have been reprinted several times. Those who are interested in his thoughts about self-representation of species (Selbstdarstellung), own appearance (eigentliche Erscheinung) etc… should try his New paths in biology (5). I will just focus on one aspect of his legacy – form development and polarization of nerve and reproductive centres in Vertebrata. This issue may be of interest because it aroused noteworthy response of some neodarwinian apologists.
Adolf Portmann didn’t dismiss natural selection as the real force in evolution. Yet he proposed processes that so to say overbridge selection, that are “above” natural selection. Natural selection can only select what is offered for selection. But biological structures offered for selection have their own logic and orientation – be it appearance, coloration of animals, form development (Formbildung) or polarization of nerve and reproductive centres in Vertebrata (6).
Portmann distinguished the head pole and the reproductive pole in animals. During evolution nerve centres moved towards one pole and reproductive organs towards another pole. Outcome of this process is most distinctly visible in Vertebrata and especially in Mammalia. Not only is the head the centre of senses, perception and often impressively adored (with horns for instance), but it is also the centre of individuality where emotions are displayed. On the other hand reproductive organs in some mammalian groups ended up in a dangerous place – outside the body.
The problem of descent of mammalian testicles should be viewed from this perspective according to Portmann. Functional neodarwinian explanation might be dismissed. Neodarwinists claim that testicles were placed outside the body because they need lower temperature to produce spermatozoa. Yet this may be just the other way around and it is only subsequent adaptation to the lower temperature. For such a statement Portmann brought up two arguments. Firstly many mammalian groups have testicles inside their bodies. Secondly birds produce spermatozoa at much higher temperature than mammals – often at 42 ˚ Celsius. None of these groups have any problems with it.
T-testicles in elephant shrew, seal and horse.
Portmann had presented his idea several times in his writings. Yet neodarwinists insisted on cooling spermatozoa hypothesis. His concept was dismissed using the argument that birds actually cool spermatozoa. Portmann was accused of unwillingness to accept extensive experimental work (7)(8). One wonders what darwinists sometimes mean under “extensive experimental work”. As it turned out later experiments no way supported their claims.
One of the latest paper about the problem was published by Werdelin and Nilsonne (1999) (9). They came to the conclusion that the problem is not descent of testicles but their ascent. Mapping scrotal, ascrotal and testicond (e.g. not descended) testicles to an outdated mammalian tree they came to the surprising conclusion that descended testicles is a “primitive condition” .This explanation seems to have been accepted also by Karel Kleisner who adressed Portmann´s view in (4). Consequently Kleisner has proposed excaptation as an explanation: once functional cooling mechanism in Eutheria has become a signalling one. Yet the problem is that Werdelin and Nilsonne conclusions do not correlate so clearly with modern mammalian phylogeny (10). Most parsimonious explanation according to the modern mammalian trees indicates that the descent could have evolved only after Monotremata, Marsupialia, Afrotheria and Xenarthra branched (9).
Doctor P.Z. Myers’ peculiar interpretation of Werdelin and Nilsonne paper as “scrotal arrangement …is primitive condition, inherited from mammal-like reptiles of the Permian” has been also dismissed by molecular biology in platypus recently. (11).
In 1997, a research was carried out on fowls which rejected “experimetal work” of Portmann’s adversaries. It turned out that fowls do not cool their testicles at all (12).
Authors of the research have asked this question:
Our data raise interesting questions relative to reproductive fitness and evolution. For example, why have most mammals evolved external (and cooler) testes, which makes the testes (and most importantly, the genetic potential they contain) much more vulnerable, while the other predominant homeothermic group, Aves, have evolved testes that function efficiently at elevated core body temperatures?
Adolf Portmann’s ideas on polarization of nerve and reproductive centres gives an interesting non-darwinian answer.
(1) in English:
Geschichte, Universität Basel
(5)in German: Neue Wege der Biologie, Piper, München 1960
(6)in German: Adolf Portmann: Dualitat der Geschlechter. Eranos Jahrbuch 1967 (Polaritat des Lebens), Rhein-Verlag Zurich 1968, page 462:
“Die Formenbildung geht über die funktionelle Notwendigkeit, über den puren Erhaltungswert hinaus.”
“Wir müssen auch darauf hinweisen, dass in der gesamten Evolution der Wirbeltiere von der Fischstufe an eine kaudale Verlagerung der Keimstätten feststellbar ist, die aber erst beim Säugetier ihre extremste Möglichkeit verwirklicht.”
“…Niemand wird die Mitwirkung der Auslese bei der Erhaltung und Umbildung bestehender Strukturen bestreiten. Was uns jetzt aber besonders angeht, ist der Entstehungsvorgang. Wir wissen zurzeit von keinem unserem Verstand zuganglichen Anlass, der das Heraustreten mannlicher Keimdrusen aus dem Schutz der Leibeshohle funktional erklart…
….die Deutung auch der Geschlechtgestalt wie der organischen Formbildungen überhaupt in einem umfassenderen Zusammenhang als dem des Erhaltungswertes zu sehen. Damit wird weder des Erhaltungsfunktionen noch der Selektionswirkung etwas von ihrem tatsachlichen Wert genommen. Es gilt, einen weiteren Horizont zu sehen, in dem das ganze der organischen Gestalt gedeutet werden muss…”
(7) Raymond Cowles : “THE EVOLUTIONARY SIGNIFICANCE OF THE SCROTUM”:
In summary it seems probable that in the aves we have a case of vertebrates, having high normal body temperatures and no external thermal regulatory scrotum, substituting for this device a system that requires nocturnal spermatogenesis when temperatures are regularly 2-3″ C. below the daytime norm and that in addition there is direct ventilation and a 2-3″ C. cooling in the air sac that partly or wholly insulates the testes from the viscera and the kidney with its massive blood flow, while permatogenesis is in progress, and that in addition sperms may be stored in an external protuberance carrying a convoluted portion of the vas deferens. Surely there is evidence here that does not agree with Portmann’s dismissal of the importance of temperature in reproduction. Portmann’s unwillingness to
accept the extensive experimental work that has been done in this field since at least as early as 1898 and continuing to the present, and his substitution of an “all or none” speculation based solely on the gaudy posteriors of apes and the ornamented posteriors of some Artiodactyles is less than convincing.
(8) Rodolfo Ruibal Uni California in the same journal as (7): THE EVOLUTION OF THE SCROTUM.
Direct evidence has been provided by Riley (1937) to show that avian spermatogenesis is sensitive to high temperatures… However, when the birds become active and raise the body tetnperautre to 110′ F. there is a complete cessation of spermatogenesis. It is clear that instead of contradicting the thermoregulatory theory, the avian condition does provide corroboration, since there is evidence of some analogous adaptation.
9) Werdelin L, Nilsonne A (1999) The Evolution of the Scrotum and Testicular Descent in Mammals: a Phylogenetic View.
J. theor. Biol. 196:61-72.
Compare their mammalian phylogeny tree here:
with a modern one here:
Marsupialia have descended testicles – but body temperature 35,5 ˚ Celsius. There is probably no clear correlation between internal/external testicles and body temperature:
* marsupialia………….35,5 ˚Celsius………..external testicles.
* gorillas………………..36,0 ˚Celsius………..external testicles.
* elephants……………..36,5 ˚Celsius………..internal testicles.
* birds often……………42,0 ˚Celsius………..internal testicles.
One has to read discussion under the article written by doctor PZ Myers, especially the ideas of Conrad Knauer . It turned out that according modern mammalian phylogeny every placental mammal with testicondy (eg.testicles not descended) is in Afrotheria. Just a quick look at modern mammalian phylogeny must persuade anyone that “scrotal primitive condition” is nowadays only a speculation.
Those who have an opportunity to read Portmann´s work in original could compare the use of language by both men. A clear, distinguished and precise thoughts of a prominent scholar vs. wanna-be witty language of a “godless liberal”.
The platypus provided the snapshot that brought the whole picture into focus: it has an LGR7-specific relaxin gene, but its other relaxin gene activates both receptors. The finding explains why platypuses keep their testicles inside their bodies-they lack a protein that specifically binds to LGR8-and also highlights the stepwise changes that must have occurred after the duplication of the ancestral gene.
12) Determination of Testis Temperature Rhythms and Effects of Constant Light on Testicular Function in the Domestic Fowl (Gallus domesticus) by CE Beaupre, CJ Tressler, SJ Beaupre, JL
Morgan, WG Bottje and JD Kirby Biology of Reproduction, Vol 56, 1570-1575:
It is apparent from the data that the testis is not cooled by association with an air sac and, indeed, is not cooled by any mechanism. Therefore, spermatogenesis occurs in the domestic fowl at the core body temperature of 40-41 C. Our results provide evidence for the uniqueness of spermatogenesis in the avian testis as compared to that of the mammals examined thus far, in which spermatogenesis occurs at 33-350 C.