Did ancient peoples transition from killing their first born children to symbolically offering them?

Question

In the Old Testament, there are a couple of verses in which the Israelites are forbidden from killing their own children as part of a religious sacrifice (not too surprising, I hope).

Do not give any of your children to be sacrificed to Molek, for you must not profane the name of your God. I am the Lord. - Leviticus 18:21

Say to the Israelites: ‘Any Israelite or any foreigner residing in Israel who sacrifices any of his children to Molek is to be put to death. The members of the community are to stone him. - Leviticus 20:2

Suppose that some of the members of the community choose to look the other way when someone sacrifices one of their children to Molek. God will take those who looked the other way, and turn them who against their families. God, will cast them out and exile them from the community of Israelites - Leviticus 20:4

The burning of goats, lambs (sheep), bulls (cows), are condoned in Exodus, Leviticus, and the Book of Numbers, but sacrificing human children is expressly disallowed.

There is also a lot of stuff in the old testament about the firstborn human children belonging to the lord.

Did tribal people living near Egypt or the Red Sea use to perform human sacrifice on occasion? Did the time of Old Testament events represent a shift in which tribal peoples turned away from that practice? Perhaos the new religious leaders re-interpreted what it meant to dedicate (offer) your firstborn child to the lord. Did the priests make new rules stating that Israelites could redeem a human child by killing a goat instead?perhaps they would offer a few shekels of silver; poe it was argued that the human lives which used to be owed to God were no longer owed because descendants of Levi would take care of the holy tent full of sacred artifacts.

Did the oral teachings pre-dating Leviticus stipulate that firstborn human children were to be offered to the lord as a sacrificial offering? Instead of repudiating the notion of sacrificing your firstborn child, did religious leaders in the time of Moses re-interpret the instruction? Did they reform religious law by allowing people to buy back (redeem) their firstborn children?

The Lord said to Moses, “Consecrate to me every firstborn male. The first offspring of every womb among the Israelites belongs to me, whether human or animal.” - Exodus 13:1, 2

You are to give over to the Lord the first offspring of every womb. All the firstborn males of your livestock belong to the Lord. You can sacrifice a young goat or lamb in place of a firstborn donkey. If you do not offer an alternative for the donkey, you must break the donkey's neck. [...] your children will ask you, "what does this all mean?" Tell them [...] I sacrifice all firstborn males to the lord, except that firstborn sons of man are bought back - Exodus 13:12-16

Redeem the firstborn donkey with a lamb, but if you do not redeem the donkey, then you must break the donkey's neck. Redeem all your firstborn sons by sacrificing an animal - Exodus 34:20

All of the firstborn are mine. When I struck down all the firstborn in Egypt, I set apart for myself every firstborn in Israel, whether human or animal. They are to be mine. I am the Lord.” - Numbers 3:13

When Pharaoh stubbornly refused to let us go, the Lord killed the firstborn of both people and animals in Egypt. This is why I sacrifice to the Lord the first male offspring of every womb and redeem each of my firstborn sons.’ - Exodus 13:15

“You must give me the firstborn of your sons. Exodus 22:29

The first offspring of every womb belongs to me, including all the firstborn males of your livestock, whether from herd or flock. - Exodus 34:19

Redeem the firstborn donkey with a lamb, but if you do not redeem it, break its neck. Redeem all your firstborn sons. “No one is to appear before me empty-handed. - Exodus 34:20

for all the firstborn are mine. When I struck down all the firstborn in Egypt, I set apart for myself every firstborn in Israel, whether human or animal. They are to be mine. I am the Lord.” - Numbers 3:13

The Lord said to Moses, “Count all the firstborn Israelite males who are a month old or more and make a list of their names. - Numbers. Take the Levites for me in place of all the firstborn of the Israelites. Moses counted all The total number of firstborn males a month old or more, listed by name, was 22,273. “Take the Levites in place of all the firstborn of Israel, and the livestock of the Levites in place of their livestock. The Levites are to be mine. I am the Lord. To redeem the 273 firstborn Israelites who exceed the number of the Levites, collect five pieces of silver for each of them give the silver to Aaron and his sons (the priests) as the redemption price for the difference in first born sons. From the firstborn of the Israelites Moses collected silver weighing 1,365 shekels, according to the sanctuary shekel. - Numbers 3:46-50

I have taken the descendants of Levi as my own in place of the firstborn, the first male offspring from every Israelite woman. Every firstborn male in Israel, whether human or animal, is mine. When I struck down all the firstborn in Egypt, I set the firstborns apart for myself. I have taken the Levites in place of all the firstborn sons in Israel. - Numbers 8:16-18

The first offspring of every womb, both human and animal, that is offered to the Lord is yours. But you must redeem every firstborn son and every firstborn male of unclean animals.- Numbers 18:15

“But you must not redeem the firstborn of a cow, a sheep or a goat; they are holy. Splash their blood against the altar and burn their fat as a food offering, an aroma pleasing to the Lord. - Numbers 18:17

Do the Levites represent a religious reform where substitutes or alternatives of sacrifices are made instead of a person's firstborn son?

Answer 1

It is indeed likely that some tribal people transitioned from killing their first born children to symbolically offering them. The practice in ancient times is well documented but virtually non-existent today, while many cultures do offer their infant children to God through ceremonies such as baptism, circumcision and other rituals. Whether the Israelites also made this transition is debatable.

The OP has provided numerous examples pf the Bible requiring the redemption of firstborn sons. But it cannot be proved from this that they were to be redeemed from a previous requirement involving human sacrifice. The first instance of the commandment to redeem the firstborn occurs shortly after the original Passover event. Rabbinical tradition see a directly correlation between the two:

When "the Lord slew all the first-born in the land of Egypt" but spared the first-born of the Israelites, the following commandment was given: "Sanctify unto me all the first-born, whatsoever openeth the womb among the children of Israel, both of man and of beast: it is mine" (Ex. xiii. 2), which is explained in greater detail in verses 12-15. The first-born of clean beasts were thus made holy and were unredeemable, while the first-born of unclean beasts and of man had to be redeemed from the priests (Num. xviii. 15-18; Deut. xv. 19-22; compare Neh. x. 37).

In other words, the Israelites were required to redeem their firstborn sons because God had taken the firstborn of Egypt, not because these sons had previously been sacrificed by the Israelites to God.

On the other hand, modern interpreters of the story of Abraham and Isaac suggest that it was popularized to help put an end to the practice of human sacrifice among the Israelites. Nor can we we be certain that the Israelites did not off their firstborn to God in the period between the patriarchs and Moses. Even much later, the fact that Jeremiah felt constrained to inform his hearers that human sacrifice had "never entered [God's] mind," (Jer. 32:35) also implies that some of those who continued the practice must have believed they were offering their sons to God.

Conclusion: while there is some theoretical basis to believe that the redemption of the firstborn replaced a previous practice of human sacrifice, this cannot be inferred with certainty from the text. The traditional explanation is that the practice of redemption originated as a result of God's taking the lives of the Egyptian firstborn, while sparing the Israelites from the same fate.

Answer 2

There is actually some evidence from the bible itself that at some point in the history of biblical interpretation it was understood that God actually commanded sacrifice of the firstborn (an obvious reference to Exodus 13).

This is what Ezekiel 20:26 says:

So I gave them other statutes that were not good and laws through which they could not live; 26 and I defiled them through their gifts—the sacrifice of every firstborn—that I might fill them with horror so they would know that I am the Lord.’

וְגַם-אֲנִי נָתַתִּי לָהֶם, חֻקִּים לֹא טוֹבִים; וּמִשְׁפָּטִים--לֹא יִחְיוּ, בָּהֶם. וָאֲטַמֵּא אוֹתָם בְּמַתְּנוֹתָם, בְּהַעֲבִיר כָּל-פֶּטֶר רָחַם: לְמַעַן אֲשִׁמֵּם

This seems to indicate that the Israelites understood some ancient law to demand the sacrifice of the firstborn, or that some laws were purposely ambiguous enough to allow for such an interpretation of Exodus 13, or some other unknown ancient code of law.

See my question here, for more sources on this and the various interpretations.