Another explanation: these are descendants, but the earlier ones are not descendants. And what were they? Spirits. For Rabbi Simon said: throughout all the hundred and thirty years that Eve was separated from Adam, the male spirits would be inflamed by her and beget offspring from her, and the female spirits would be inflamed by Adam and beget offspring from him. This is what is written: "When he commits iniquity, I will chasten him with the rod of men and with the afflictions of the sons of men" (II Samuel 7:14) - meaning the offspring of the first man.
Adam's Descendants
Bereshit Rabbah 24:6
דָּבָר אַחֵר, אֵלּוּ תּוֹלָדוֹת וְאֵין הָרִאשׁוֹנִים תּוֹלָדוֹת, וּמָה הֵן רוּחוֹת, דְּאָמַר רַבִּי סִימוֹן כָּל מֵאָה וּשְׁלשִׁים שָׁנָה שֶׁפֵּרְשָׁה חַוָּה מֵאָדָם הָיוּ רוּחוֹת הַזְּכָרִים מִתְחַמְּמִים מִמֶּנָּהּ וְהָיוּ מוֹלִידִים מִמֶּנָּהּ, וְרוּחוֹת נְקֵבוֹת מִתְחַמְּמוֹת מֵאָדָם וּמוֹלִידִים מִמֶּנּוּ. הֲדָא הוּא דִכְתִיב: אֲשֶׁר בְּהַעֲוֹתוֹ וְהֹכַחְתִּיו בְּשֵׁבֶט אֲנָשִׁים וּבְנִגְעֵי בְּנֵי אָדָם, בְּנוֹי דְּאָדָם קַדְמָאָה.