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 the larger Indo-European language family. Although the Hittites are placed in the 2nd millennium BCE, the Anatolian branch seems to have separated at a very early stage from Proto-Indo-European, or may have developed from an older Pre-Proto-Indo-European ancestor. If it separated from Proto-Indo-European, it likely did so between 4500–3500 BCE. The archaeological discovery of the archives of the Hittites and the belonging of the Hittite language to a separate Anatolian branch of the Indo-European languages caused a sensation among historians, forcing a re-evaluation of Near Eastern history and Indo-European linguistics. In accordance with the Kurgan hypothesis, J. P. Mallory notes