Alma 31:8-11

8  Now the Zoramites were dissenters from the Nephites; therefore they had had the word of God preached unto them.

9  But they had fallen into great errors, for they would not observe to keep the commandments of God, and his statutes, according to the law of Moses.

10  Neither would they observe the performances of the church, to continue in prayer and supplication to God daily, that they might not enter into temptation.

11  Yea, in fine, they did pervert the ways of the Lord in very many instances; therefore, for this cause, Alma and his brethren went into the land to preach the word unto them.

Alma 31:8-11 (Emphasis mine)

Mormon breaks in and gives us some information about the Zoramites.  We get a few examples: 

They did not keep the commandments and statutes of God.

They did not accept the law of Moses.

They did not pray daily asking they not enter into temptation.

In short, they perverted the ways of the Lord.  This is why Alma(2) led his “missionary all-star team” to preach the gospel to them.

18  ¶ He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God.

19  And this is the condemnation, that light is come into the world, and men loved darkness rather than light, because their deeds were evil.

20  For every one that doeth evil hateth the light, neither cometh to the light, lest his deeds should be reproved.

John 3:18-20 (Emphasis mine)

John Twedtnes gives us more information about the Zoramites.

“I have proposed elsewhere that the tribal affiliations of Book of Mormon peoples remained part of their culture even during times when various peoples merged. This does not preclude the adoption of other peoples into these cultures. Thus, the Zoramites whom Alma and his companions sought to recover (they being ‘dissenters from the Nephites,’ Alma 31:8) may have been descendants of the original Zoramites (Jacob 1:13) as well as others who merged with them. See John A. Tvedtnes, ‘Book of Mormon Tribal Affiliation and Military Castes,’ in Warfare in the Book of Mormon, ed. Stephen D. Ricks and William J. Hamblin (Salt Lake City: Deseret Book and FARMS, 1990), 296—326.” [1]  (Emphasis mine)

John Sorenson speculates that we see an indirect example of people being here before Lehi and company arrived.

“One of these statements occurs during the visit by Alma and his seven companions to the Zoramites. ‘Now the Zoramites were dissenters from the Nephites’ (Alma 31:8). As Alma prayed about this group, he said, ‘O Lord, their souls are precious, and many of them are our brethren’ (Alma 31:35). We may wonder about those whom they considered not their ‘brethren.’ Apparently he was speaking of those who were neither Nephites, Lamanites, nor ‘Mulekites.’ People in all those three categories are referred to in the text by Nephites as ‘brethren ‘ (see, for example, Mosiah 1:5 and 7:2, 13 and Alma 24:7–8).” [2]  (Emphasis mine)

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[1] Reinventing the Book of Mormon (footnote 20), John A. Tvedtnes, Provo, Utah: Maxwell Institute, accessed November 22, 2011.

[2] When Lehi's Party Arrived in the Land, Did They Find Others There? John L. Sorenson, Provo, Utah: Maxwell Institute, accessed November 22, 2011.