Mormons tend to assume that Lehi arrived here in the Americas with a great number of people. Let's look at what the Book of Mormon has to say about that and the number of people that could have come here to start this civilization.
Lehi and his family left Jerusalem in 600 B.C. Definite date is given in 1 Nephi 2:4.
How old would Lehi's children have been when they left? Remember they carried all their belongings, provisions and their tents with them. No mention is made of any pack animals nor camels. (1 Nephi 2:4). They traveled for three days away from Jerusalem. (1 Nephi 2:6) Nephi sent back to Jerusalem packing his tent. (1 Nephi 3:9). Nephi claims to be "a man large in stature..." (1 Nephi 4:31) How old could this "man", Nephi, be? Being the youngest son at the time, he could not have been more then 20 years old in 598 B. C. And let's say that there is 18 months between the other brothers. That would make Sam about 21 1/2, - Lemuel about 23, -Laman 24 1/2.
All of these men married in the same year, including Zoram. (1 Nephi 16:7)
Zoram took the oldest of Ishmael's daughters (#1)
Laman took #2
Lemuel took #3
Sam took #4
Nephi took #5
The year is now somewhere around 596 B. C. That would make Nephi about 22 years old. Their "women did bear children in the wilderness." They "ate raw meat... their ...women gave plenty of suck for their children, and they were strong ...even like unto the men." (1 Nephi 17:2) The oldest of these children would have been only 3-4 years old by 592 B.C. They have been in the wilderness for 8 years now. (1 Nephi 17:4). See definite date notation at bottom of page. They arrive at the seashore, 1 Nephi 17:5,6. Still using the 18 months between children, the ages would be 4, 2 1/2 down to infants. So assuming that all these women had children accordingly, there would now be 13 children under 4 years of age. Also during these years Lehi had two more sons, so they also would be under 8 years of age. So we now we have maximum 15 children (including Lehi's two sons born in the wilderness) and 18 adults. Mention of Nephi's sisters doesn't come till later. Their ages are unknown. We'll assume that they are younger than Nephi and older than Jacob and Joseph who were born in the wilderness.
Nephi is commanded to go up to the mountain and meet with God. (1 Nephi 17:7) There he is told how to build a ship and make the tools to build it with. (1 Nephi 17:8-11).
In verse 10 and 16 he is told where to find ore and from that ore he makes the tools with which to build the ship. Nephi has 18 adults and several 4-year olds to help him mine, smelt and manufacture the tools. Not to mention gathering food etc. (See Metallurgy and the Book of Mormon on this site).
1 Nephi 18:4 states that they completed the building of the ship. The date at the bottom of the page is 591 B.C. So it has taken them about one year or more to mine the ore, smelt it, manufacture the tools, harvest the timber and construct the ship, in addition to gathering food for these people. By verse 8 they are setting sail for the promise land and the year is now 590 B.C. The oldest children are now about 5-6 years old.
An interesting side question, where did they get the material to make the sails?
Verse 23 relates their arrival at the promise land and pitching their tents. After the temporary mutiny at sea and the loss of forward sailing, time has passed. The date given at the bottom of the page is 589 B.C. The oldest of the children are now 6-7 years old.
Verse 24 tells about them immediately tilling the land and planting the seeds they had brought with them. Remember these seeds have lain dormant now for years and years since they left Jerusalem. Depending on what seeds they brought and planted, it usually takes 4-6 months for a crop to mature and be harvested. Now that they have harvested a good crop, they have time to explore. It is amazing what they find.
Verse 25 mentions all kinds of wild beasts, wild goats, and all manner of wild animals, but cows, oxen, asses, horses, goats (domesticated?) which were for the use of men.
Another question to ask here is: Who was there in the new promise land that was knowledgeable enough to take a full grown bull and castrate it to make it an ox, and for what purpose was it done then?
Also, in verse 25, it is stated that they found "all manner of ore, both of gold, and of silver, and of copper.
The very next thing Nephi does at the command of the Lord, is to make plates of this new found gold ore to make a record of his people. (1 Nephi 19:1-4).
The year is now between 588 and 570 B.C. and the oldest of the children can be from 16 years old down to infants, possibly. Half of all these children are girls. (In the year 580 Nephi would be 38-40 years old).
So now (in the year 580) the total population of this group, at maximum, would be 16 older adults. Ishmael has died (1 Nephi 16:34). (Lehi dies in 2 Nephi 4:12). These men have been married for about 16 years now. Zoram married Ishmael's oldest daughter. They have only one son. Laman married Ishmael's # 2 daughter. The maximum number of children at this point with single births would be 11 per couple based on the number of years they have been married and based on having one child every 18 months.
Lemuel would be the same. (11)
Sam would be the same. (11)
Nephi would be the same. (11)
Nephi had "sisters" but no mention is made of them marrying.
Total number of children would be 45, maximum during those 16 years. Not discounting those that may have died at birth or from disease or illness. The oldest of these being 15 years old.
Seven of the adults are women. Two are elderly. (Lehi's and Ishmael's wives). The other women are nursing mothers and their hands are full taking care of the other smaller children. That leaves only Nephi's sisters to help with other tasks.
In 2 Nephi 5:5, 6 Nephi is told to flee into the wilderness and take all those who would go with him. He takes his older brother Sam and his two younger brothers Jacob and Joseph and his sisters. "And all those who would go with me." The maximum number of people in Nephi's group would then be 35, most of them very young. The remainder would go with Laman and Lemuel.
After they traveled in the wilderness for many days they set up their tents. (v. 7.) Then they sowed their seeds and "reaped in abundance". "And began to raise flocks, and herds, and animals of every kind." (v. 11.)
They have been in the promise land for 8-9 years and have "flocks, and herds and animals of every kind." They have been able to domesticate all these animals in that time period. We are still using 580 B.C. as the mid point date in this examination.
Let's re-examine the numbers again. The group has split. Laman and Lemuel, their wives and maximum of 22 children, along with the sons of Ishmael (total number 28) cause Nephi to flee into the wilderness.
There, in this wilderness, Nephi makes multiple swords "after the manner of the sword of Laman." (2 Nephi 5:14) This was for protection from the evil brothers, Laman and Lemuel and their group, "lest by any means the people who were now called Lamanites should come upon us and destroy us". Again the question has to be asked: From where did he get the ore and how did he refine it with a bunch of teenagers and small children?
2 Nephi 5 continues by stating that they worked at building all manner of buildings, they worked in wood, iron, copper, brass, steel, gold, silver, and other precious metals. Nephi states that his group built a temple "after the manner of the temple of Solomon." Then he continues by saying that it wasn't quit as nice as Solomon's because all those precious things "were not to be found upon the land." But "the workmanship was exceeding fine." (vs. 15,16.) They did all this, in addition to raising their "flocks and herds," gathering food for their families, mining for precious metals, refining them, and fighting off Laman and Lemuel in their attacks on the Nephites?
If we use the date at the end of the chapter, which is 559, Nephi is about 59 years old. The children are now grown. Who are they marrying?
One does not need to go any further to realize that this is a fabricated story.