Indo-European copula copula (with corresponding voiceless and voiced fricatives) existed side by side in Germanic, and the involvement of a separate root "" is unnecessary. The root "*(s)teh-" meant "to stand". From this root comes the present stem of the so-called "substantive verb" in Irish and Scottish Gaelic, "tá" and "tha" respectively. On the absence of the initial s- in Celtic, see Indo-European s-mobile. In Latin, "stō, stare" retained the meaning "to stand", until local forms of Vulgar Latin began to use it as a copula in certain circumstances. Today, this survives in that several Romance languages (Galician-Portuguese, Spanish, Catalan) use it
Indo-European migrations extended the Indo-European culture zone east of the Ural mountains, giving rise to Proto-Indo-Iranian and the subsequent spread of the Indo-Iranian languages toward India and the Iranian plateau. According to Anthony, steppe herders, archaic Proto-Indo-European speakers, spread into the lower Danube valley about 4200–4000 BCE, either causing or taking advantage of the collapse of Old Europe. According to Anthony, their languages "probably included archaic Proto-Indo-European dialects of the kind partly preserved later in Anatolian." According to Anthony their descendants later moved into Anatolia, at an unknown time, but maybe as early as 3,000 BCE. According to Mathieson & Reich et