Persian, Dari, Tajik: من اینجا هستم

[PersoLatin]

In Iranian Persian I am here is, من اینجا هستم and است is only used for the third person singular i.e. او اینجا است or او اینجاست, for the rest هستم، هستی، هستیم، هستید and هستند ‌are used, I believe this is inconsistent & wrong, assuming I am I right, when & why did this happen?

I have heard that the equivalent terms in Dari & Tajik Persian (perhaps within Iran too) are استم، استی، است استیم، استید، استند, is that the case?

Examples:
هستن - There is an apple there/در انجا یک سیب هست
استن - That is an apple/این یک سیب است

So هستن should not be used in straight forward cases like: من اینجا هستم (I am here) or ما پرستار هستیم (we are nurses) and من اینجا استم and ما پرستار استیم should be.

 

[Derakhshan]

In Middle Persian you had only ast which was both the verb 'to be' in the 3rd person singular, and was used to express 'there is/exists'. I recall reading that the initial h- in هست may have come from the Middle Persian copula for 'to be', which were hēm, hē, hēnd, ... for hastam, hasti, hastand, ...

You may think -am, -i, -and in New Persian are the shorthand for hastam, hasti, hastand but as far as I know, they are older than the latter forms.

ast/bud was also used to express possession:
man waččag ast = I have a child.

And this continued into Early New Persian:
وی‌را بنده‌ای بود فتح نام = He had a slave named Fath.
-Qābusnāme

In Larestani ast/hast continues to be used in this way, a similar example:
hem banda-š haste = He has a slave.

 

[fdb]

In Middle Persian the copula is:

hem hē ast hēm hēd hend

The /h/ is etymological in all persons except 3 sing. (Cf. Skt asmi, asti; OP ahmi, asti etc.)

At some stage /h/ spread by analogy to 3 sing. hast. Then (in Early New Persian) this was reinterpreted as a verbal stem giving the paradigm:

hastam hastī hast hastēm hastēδ hastand

with semantic differentiation between the copula ast and the existential verb hast.

In most Afghan Persian dialects (including that of Kabul) historic /h/ is lost in all positions, with the result that the distinction between ast and hast is neutralised. This spills over into the written language, at least in Afghanistan.