Rabbinic Jews are NOT the Oldest Sect of Practicing Jews!
The Samaritan Jews of Shechem (Nablus, in modern-day Israel) have maintained parts of the most ancient Jewish traditions. One pristine example of this continuity can be seen in the interesting rituals of Samaritan Jews during the season of Passover. Since some may question my credibility in discussing such a controversial issue, I will submit the opinion of a more trust-worthy Jewish scholar. I came in contact with the work of Hayyim Schauss during my graduate studies at Spertus Institute of Jewish Studies in Chicago. The citation is rather lengthy, but I believe you will find his comments to be informative.
There are, however, in our own day, groups of Jews that never came in contact with the masses of the Jewish folk . . . They, therefore, observe Pesach (Passover) exactly as it was observed two to three thousand years ago. Such Jews are the Samaritans of the city of Nablus. . . .
. . . Modern historical research has proved that the Samaritans are not descendants of the heathen colonists settled in the northern kingdom of Israel by the conquerors of Samaria, as was once assumed. Nor are they to be identified with Nehemiah’s opponents of the Persian period. Actually, the Samaritans of today are a small and poor remnant of an old and great Jewish sect that appeared in Palestine about the beginning of the Greek period. They form the oldest Jewish sect in existence. They were always strongly religious Jews who believed in one God and strictly observed the Law of Moses. . . .
. . . In the days of the second Temple almost the entire central part of Palestine, between Judah and Galilee, was thickly populated with this Jewish sect of Shechem; there were also many followers of the sect in southern Syria and in other eastern lands. Today, however, there are barely two hundred left, they speak Arabic and inhabit a special quarter in Nablus. They have a synagogue there and a High Priest, who is their teacher and spiritual leader.
The ritual practices maintained by the Samaritans during Passover are readily acknowledged to be most similar to the practices of biblical Judaism.
Probably the closest approximation of a Passover ceremony in Biblical times is the Seder held each year by the Samaritans on the stony top of Mount Gerizim. . . . The Samaritans claim unbroken descent from the family of the High Priest Aaron, but because of an ancient schism, they were not admitted as Jews by the Temple authorities. 
Do Some Jews Still Practice Animal Sacrifices?
Yes! This may shock many readers, nevertheless, the practice of offering sacrifices within Judaism is not completely dead. Consider the Passover practice of modern Samaritans. The sacrifice continues as an important aspect of their tradition and religious practice.
For their Seder, the Samaritan families assemble on their mountaintop. Selected sheep are sacrificed by the sacerdotal leaders.
The ancient practice is staunchly ignored by most modern Jews. Perhaps this is because the concept is abhorrent to sophisticated, cultured, educated Jewish folk. More likely, the practice fails to fit into the rabbinic view that the sacrificial requirements of Scripture have been arbitrarily discontinued. Reality has prohibited Jewish people from fulfilling the requirements of the Mosaic Law in accord with Levitical standards. The dilemma caused by the destruction of the Temple has not entirely stopped the Samaritan Jews. This is due to the fact that they reject rabbinic leadership and “deny the sanctity of Jerusalem.” 
Although the Samaritan sacrifices are restricted to Passover, they continue to offer that sacrifice.
Samaritans observe Pesach to this day on Mount Gerizim, in a manner that other Jews ceased practicing thousands of years ago. The custom of offering sacrifices has died out with the Samaritans, except on the fourteenth day of Nisan, when they offer the ceremonial Pesach sacrifice.
It has been argued by various scholars that the Samaritans practice their ancient form of Judaism because they have not been influenced by later forms of Jewish practice developed in subsequent generations by leaders of the rabbinic movement. Since they live in such proximity to the culture and influence of present day Israel, it seems likely that some influence must have occurred to “corrupt” their original ancient practice. The Samaritans are not the only Jews to have maintained a sacrificial practice.
It can be shown that another group of Jews were not influenced by the rabbinic leaders during the centuries following the Jewish war with Rome. Like the Samaritans, the Falashas of Ethiopia also maintained a sacrificial tradition.
Falashas: Black Jews of Ethiopia
An entire history of Jewish practice, apart from rabbinic Judaism, can be identified in the practices of the Ethiopian Falashas. Most of these Jews now live in Israel, but their former practices are of great interest to some students of Judaism.
Their practices, beliefs, and traditions may predate all forms of rabbinic Judaism. Theories abound suggesting that their practices date back to the times of Jeremiah (626 BCE), or even as far back as the reign of Solomon (970 BCE). Intrigue and mystery surround some accounts that seek to prove that the ancient lost Ark of the Covenant has resided among the Jews of Ethiopia since Solomon’s involvement with the Queen of Sheba. Regardless of the location of the lost Ark, the “lost Jews” of Ethiopia offer an incredible postscript to the history of Judaism. Investigations during the last century help date the disconnect of their relationship with the Jews of ancient Israel.
The Falashas know nothing of either the Babylonian or the Jerusalem Talmud, which were composed during and after the time of the captivity. They also do not observe the Feasts of Purim and the Dedication of the Temple, which . . . are still solemnly kept by the Jews of our time.
These holidays, Hanukkah and Purim, give a deep sense of continuity to the Jewish struggle for survival. The Falashas have survived without these festivals. This is important because Hanukkah has been celebrated throughout Judaism as a post-biblical holiday since the middle of the 2nd century BCE. Purim celebrations honoring Queen Esther are even older dating back to the 5th-6th century BCE. Since the Falashas knew nothing about these festivals (which are well known to Jews in Israel and throughout the rest of the Diaspora), it is altogether likely that the Ethiopian Jews were practicing their faith for many centuries before the festivals were added by rabbinic Jewish leaders.
What important factor separates this ancient sect of Judaism from the faith of the rabbis? Sacrifices! The Falasha Anthology which was originally published for The Yale Judaica Series contains fascinating details about the religious literature of Ethiopian Jews. Herein, the author, a former professor at Brandeis University, offers a firsthand account.
An important religious practice of the Falashas is sacrifice. In the region I visited sacrifices are offered only once a year, namely on the fourteenth of Nisan, on the eve of Passover. . . . It seems that in other localities they also offer sacrifices at other times and on other occasions. . . . The Falashas offer sacrifices on an altar or “area of sacrifice” . . . located in the compound of the synagogue at the north side.
The animal . . . must meet the requirements of the Old Testament, i.e., it must not be blind, lame or possessed of any other corporal defect.
Modern Jews & Ritual Slaughter
If ritual animal slaughter seems violent, it is only because we are not accustomed to seeing things die. In pioneer days, family farms were the norm and people regularly killed what they ate. The Temple priest merely did it in a fashion that was a humane method of killing an animal. Observant Jews still eat kosher meat that insures the animal was killed under regulated conditions.
Kaporos: Watch out KFC!
A need for a sacrifice lives within the Jewish psyche. The rabbis may have revamped God’s regulations but the heart of God’s people have always responded to their instinctive need for a sin-bearer. Some Jews still perform an old ritual known as kaporos. The ceremony may seem primitive as it harks back too closely to the sacrifices which God demanded for forgiveness during the Temple era. Consider what one respected Jewish scholar says.
The second day before Yom Kippur has special significance in that it is the day of Kaporos. . . . The men use roosters for the ceremony and the women use hens. When the family is large, it is rather expensive to supply a fowl for each member of the family, so money is used instead. . . . First the fowl, or the money, is held in the hand and everyone reads selections from certain Psalms, beginning with the words, “Sons of Adam.” Then the fowl is circled about the head nine times, the following being recited at the same time: “This is instead of me, this is an offering on my account, this is in expiation for me; this rooster, or hen, shall go to his, or her, death (or, this money shall go to charity), and may I enter a long and healthy life.”
The ten days of penitence are not sufficient to list all of my sins. I am certain that neither fasting, nor reciting rote prayers from a book, nor even waving a chicken over my head will atone for my sins. Admittedly, I believe I need a more perfect expiation, or atonement for sin. Certainly, this is a personal matter and you may see things differently. I believe that we would still have our sacrifices if we still had our Temple. Neither the A.C.L.U. nor the A.S.P.C.A. would hinder our priestly practice because the Hebrew Bible offers no forgiveness without a sacrifice.
 This is likely due to the fact that Scripture rarely discusses the Ark after Solomon’s reign. For a more thorough discussion of the theory that the Ark of the Covenant was secretly taker to Ethiopia, consider Graham Hancock’s book The Sign and the Seal, (New York, A Touchstone Book, 1993),