From the time of Herodotus a minority of geographers have rejected the three-continent system (Europe, Africa, Asia) on the grounds that there is no substantial physical separation between them.
fɹʌmðə tˈaɪm ʌv hɪɹˈɑːdəɾəs ɐ maɪnˈɔːɹᵻɾi ʌv dʒɪˈɑːɡɹəfɚz hæv ɹᵻdʒˈɛktᵻd ðə θɹˈiːkˈɑːntɪnənt sˈɪstəm jˈʊɹɹəp, ˈæfɹɪkə, ˈeɪʒə ɔnðə ɡɹˈaʊndz ðæt ðɛɹ ɪz nˈoʊ səbstˈænʃəl fˈɪzɪkəl sˌɛpɚɹˈeɪʃən bᵻtwˈiːn ðˌɛm.