We do not inherit sin
Ezekiel 18:20 "The soul that sinneth, it shall die. The son shall not bear the iniquity of the father, neither shall the father bear the iniquity of the son: the righteousness of the righteous shall be upon him, and the wickedness of the wicked shall be upon him."
We do not inherit sin, as you can see from the verse above.
Animals die but this does not make them SINNERS. They only get the effects like the mother who has the sin of smoking. The baby will suffer the consequences but the sin of smoking is not transferred.
Romans 5:12-13,18 (ESV)
12 Therefore, just as sin came into the world through one man, and
death through sin, and so death spread to all men because all
sinned— 13 for sin indeed was in the world before the law was
given, but sin is not counted where there is no law.
18 Therefore, as one trespass led to condemnation for all men, so one
act of righteousness leads to justification and life for all men.
Thoughts on verse 12
Note that the death being talked about here is eternal death--not temporal. Verse 12 says just as sin came into the world through one man... before Adam sinned there was no sin. So sin came into the world through Adam. Note that verse 12 says nothing about that sin (of eating the fruit) being inherited. Verse 12 goes on to say 'and death by sin; that is, death (eternal) has entered into the world of men by sin. the last part of verse 12 says, and so death spread to all men because all sinned, that is Eternal death has spread to all men because they have chosen to transgress the law of God contrary to the usual thinking that death spread unto all men because Adam sinned.
Thoughts on Verse 18
verse 18 includes choice. I am sure no serious Christian holds to the doctrine that all people whether they like it or not are justified at birth because Jesus died for them. So why do people hold on to the doctrine that all people whether they like it or not are born sinners and condemned.
Adam's sin does not separate us from God
Isaiah 59:2 But your iniquities have separated between you and your
God, and your sins have hid his face from you, that he will not hear.
We are not born separated from God at birth because of Adam's sin. God separates Himself from us because of our own sin (DON'T BLAME ADAM). If Adam's sin separates from God then David was lying when he wrote:
Psalms 22:9-10 But thou art he that took me out of the womb: thou didst
make me hope when I was upon my mother's breasts. 10 I was
cast upon thee from the womb: thou art my God from my mother's belly
Psalms 71:5-6 For thou art my hope, O Lord GOD: thou art my trust
from my youth. 6 By thee have I been holden up from the womb: thou
art he that took me out of my mother's bowels: my praise shall be
continually of thee.
The issue about Jesus
Another argument concerns Jesus. Most people want to ignore it but they mustn't. This is salvation we are about here. If Jesus was born of a woman then surely He was born a sinner.
I remain convinced He was born in sin but was not a sinner just as He was born into this sinful world but committed no sin. For He was in the flesh but did not yield to the flesh having condemned it, Romans 8:3.