First man

Er is the first son of Judah

^{Gen 38:3} And she conceived, and bare a son; and he called his name Er.

Er is the first man

Adam is the first man

Reputation is that he was alive from the dust

Adam was made alive from the dust

^{Gen 2:7} And the LORD God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul.

^{Ge 38:3} and he called his name Er.

Er was 'alive from the dust'

Adam died the day he sinned.	^{Gen 2:17} But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die.
Er died because he sinned.	^{Gen 38:7} And Er, Judah’s firstborn, was wicked in the sight of the LORD; and the LORD slew him.

The story of Tamar shows the fulfillment of the Leverate law. In it Er, playing the part of Adam, dies without living (spiritual) heirs.