Anniversario della nascita di Gideon Mantell

Davide Bertè 28 gennaio 2011

Gideon_MantellGideon Mantell, nato il 3 febbraio 1790, era figlio di un piccolo commerciante ma discendente di una nobile famiglia decaduta e nutrì fin dall’infanzia una passione per i fossili.

Le cave del Sussex (Inghilterra meridionale) furono i primi luoghi in cui cominciò a raccogliere ammoniti. A diciassette anni, dopo la morte del padre, venne mandato a Londra per studiare medicina.

Qui ebbe modo di conoscere James Parkinson (che più tardi divenne famoso per la scoperta del morbo che ancora oggi porta il suo nome) che era un appassionato geologo e metteva in discussione l’età della Terra (all’epoca ritenuta di poche migliaia di anni).
Gideon Mantell, una volta laureatosi, fu preso a tempo pieno dal mestiere di medico di campagna ma nel poco tempo libero studiava la geologia della regione.

La professione medica gli permise di avere un buon sostegno economico che gli consentì di sposarsi e comprare una grande casa in cui tenere la sua collezione di fossili sempre più grande.
Presi accordi con la cava di Cuckfield (Cretaceo Inferiore), si faceva spedire i fossili che venivano ritrovati dagli operai; da questa cava cominciarono a uscire ossa gigantesche e poi il dente di un grosso rettile… non si aveva idea di che cosa potesse trattarsi; l’unico rettile fossile di grandi dimensioni conosciuto all’epoca era l’Ichthyosaurus (scoperto nel 1811), ma il ritrovamento di piante tropicali associate alle ossa gigantesche faceva pensare a un ambiente totalmente diverso. Mantell si trovava di fronte a qualcosa di completamente nuovo: un gigantesco rettile vegetariano! Nulla di simile era mai stato scoperto in precedenza e non si sapeva come interpretare il reperto…
Nel 1821 conobbe Charles Lyell, il famoso geologo, che lo mise al corrente che nel frattempo a Londra era stato esposto un fossile di un rettile gigantesco trovato da Buckland e che Georges Cuvier, a quel tempo la massima autorità nel campo dell’anatomia comparata, aveva dato il suo parere favorevole. Incoraggiato dalle recenti scoperte nel 1822 diede alle stampe Fossili delle South Downs in cui descriveva le lucertole fossili che aveva ritrovato. Pochi mesi dopo l’uscita della sua opera presentò il suo dente fossile alla Geological Society ma venne liquidato dagli “esperti” come di scarso interesse e interpretato come il dente di qualche pesce gigante. Mantell, che aveva una formazione da autodidatta non godeva del prestigio necessario per essere ascoltato seriamente.
Aiutato dall’amico Lyell fece un ulteriore sopralluogo alla cava che avvalorò le sue ipotesi; presentò quindi una lettera alla Geological Society in cui affermava con rinnovata convinzione di avere scoperto resti fossili di grandi rettili erbivori e carnivori. Ma quando Cuvier visionò il dente che Mantell aveva trovato lo determinò come un incisivo di rinoceronte (un grosso errore, come vedremo…). Mantell si ritrovò senza riconoscimenti, ad avere speso molti soldi per i cavatori che gli fornivano i fossili, il suo libro era in perdita e ad avere sprecato molte notti nello studio dei fossili: un brutto colpo.

Iguanodon e MantellTuttavia, senza lasciarsi scoraggiare dall’ostracismo della scienza ufficiale, continuò i suoi studi e nel 1824 diede il nome al gigantesco rettile vegetariano che aveva ritrovato e lo chiamò Iguanodon (=denti da iguana). Lo stesso anno uscì Ricerche sulle ossa fossili di Cuvier in cui l’autore ammetteva il suo errore precedente: Mantell era adesso pienamente rivalutato e gli venne offerto di far parte della Geological Society.
Nel 1829 ipotizzò per primo l’esistenza di un’Età dei rettili precedente all’Età dei Mammiferi. Come si può ben immaginare la sfere ecclesiastiche non furono proprio entusiaste…
L’anno seguente in una cava venne scoperta una nuova lucertola gigante, lavorando di notte per estrarla dalla roccia (Gideon Mantell di giorno continuava a praticare la professione di medico) scoprì una nuova specie che chiamò Hyleosaurus.
Nel 1834 il ritrovamento di uno scheletro parziale di Iguanodon diede nuovo supporto alle teorie di Mantell, Leggi tutto “Anniversario della nascita di Gideon Mantell”

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