Abstract

Fordyce posited that the Oligocene radiation of Odontoceti and Mysticeti was linked to the opening of Drake’s Passage between South America and Antarctica and the resultant full establishment of a circum-Antarctic current.¹ In his view, the breakup of Gondwana secondary to the shifting of Earth’s tectonic plates promoted the productivity of planktonic species, triggering rapid diversification of cetacean species marked by novel life strategies that included filter-feeding. However, in my view, that hypothesis is untenable, for an increase in food supply should lessen intraspecific competition and, therefore, decrease, not increase, rates of evolutionary change.

An alternative hypothesis would recognize first that euphausiids, commonly called krill, contain concentrations of fluoride an order of magnitude greater than those known to drastically reduce lactation in F₁-generation females and predispose premature death in their progeny when in the feed of domesticated Bovidae.^2-4 A related observation is that those deaths which occur in exposed F₂ generations appear attributable to accelerated attrition of teeth compromised by defective enamel.^5-7 One consequence is a predisposition to starve secondary to impaired amelogenesis during fetal and neonatal development. These findings are relevant because extant bovids, like cetaceans, fall within the Cetartiodactyla and are extremely sensitive to fluoride when compared with birds, horses, swine, and carnivores.⁸

The emergent question, then, is whether today’s mysticetes, which, in many cases, prefer to feed on euphausiids, are the result of a cladogenic process whose root evolutionary cause was fluoride poisoning.⁹

My corresponding mechanistic hypothesis holds this to be so. It recognizes inter alia that population expansion of a raptorial ancestral species targeting fish and cephalopods probably led to desperate exploitation of otherwise unattractive prey items of small size, including krill, by less powerful conspecifics. This merely invokes the two Malthusian postulates underpinning Darwinian theory. These predict depression of average per capita food supply and creation of a starving, or semi-starved “lower” class.¹⁰ Consequently, it follows that desperate ingestion of krill could well explain why some ancestral cetaceans lost their dentition, as the main pathogenic effect of fluoride is on calcification and, in particular, amelogenesis, not formation of the hard keratin that comprises baleen.

The principal empirical support for this hypothesis includes the finding of extremely high concentrations of fluoride in the skeletons of fin whales (Balaenoptera physalus)³ and the finding that high concentrations of fluoride not only occur in the bones of bowhead whales (Balaena mysticetus) but are accompanied by histological changes considered pathognomonic for fluoride toxicosis.* These observations indicate that fluoride is assimilated from dietary sources and distributed systemically in two representative mysticetes whose tooth germs are resorbed⁹ during prenatal life. They also imply that extant baleen whales either are not or are no longer susceptible to the catastrophic effects of high dietary fluoride on lactation clarified by the analysis of Eckerlin et al.² So, I hypothesize formally that fluoride intoxication was responsible for splitting Cetacea into its two taxonomic suborders, Odontoceti and Mysticeti.

*Eckerlin R and Krook L. Personal communications.

Dedication

This contribution is dedicated to the memory of my late colleagues Donald Abt, Richard Eckerlin, Lennart Krook, Ronald Landy, Seiji Ohsumi, Páll Pálsson, and Sam Ridgway.

Acknowledgments

I acknowledge, with sincere thanks, Dr. Páll Pálsson, Chief Veterinary Officer of Iceland, who first brought to my attention the high fluoride concentrations in the bone of baleen whales, and T.A. Albert, R.H. Eckerlin, M.C. Fossi, L. Krook, W.C. Lancaster, R.B. Landy, W.F. Perrin, C.A. Potter, and F.C. Whitmore for relevant scientific discussion. The personal communications from Drs. Eckerlin and Krook, Cornell University College of Veterinary Medicine, were based on their analyses of samples of bowhead whale bone I collected with the assistance of Winston Lancaster under authority of NOAA/NMFS Permit 519 held by Dr. Tom Albert, Department of Wildlife Management, North Slope Borough, Barrow, Alaska. The permission of Inuit whale hunters to take those samples is greatly appreciated.

*Presenting author

Literature Cited

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2.  Eckerlin RH, Maylin GA, Krook L. Milk production of cows fed fluoride contaminated commercial feed. Cornell Vet. 1986;76:403–414.

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